(OK, so this is not technically a technical issue. So sue me.)
I had the good fortune of going to Japan recently, with somebody else paying the bills. As a Fortune 500, it was their policy to fly business class on any flight over 6 hours, and I was not going to complain.
On a whim, I upgraded myself on the outbound flight to first class. It was about $650 for the upgrade as a last-chance, while-you-are-checking-in sort of thing. I figured that I'd never get another chance to fly first class for 12 hours for $700, so I took it.
As it happened, the flight back was full so I was demoted to "only" business class. As the two flights were five days apart, I can now say for sure what the differences are:
Not much, but some.
Both flights were Boeing 777-200s, with 8 first-class seats and 40 business class. The following probably won't apply to other types of jets, unless they are of comparable class. Certainly not the little Skywest commuters that have seats from hell, regardless of fare type.
Both fares have priority boarding, lounge access, and just generally better service. When my first connection was delayed 90 minutes, United had an employee at my arrival gate to make sure I made my overseas flight on time. Every other flight to Japan for the next three days was booked solid, so I appreciated this quite a lot.
(Plus a raspberry to Skywest for making me fret about my connection for two-plus hours. If it wasn't for the change of time zone I'd have missed my Japanese business meetings completely - all other flights were fully booked.)
As far as I know, both fare classes get identical lounge access.
Outbound I had no chance to try to lounges. Returning from Japan, the
lounge we were in had free booze, while once we got to the USA the
lounge there did not. I don't know why exactly - might have been
because it was the 'domestic' lounge rather than the 'international'
one, but I'm not really sure. Ask United first if you really care.
After boarding you find your seat. Basically, in first class you get a little podule thing, all by itself, not connected to another seat. It's sort of a semi-private room, in a way. It's reasonably spacious, the sides/walls are tall, and and your "neighbors" are pretty far away from you and easy to ignore.
You get lots of storage all to yourself, a big fold-flat chair, a TV, two pillows (a big and a small) and a blanket, a power plug and noise-cancelling headphones. The TV has VOD and movies, and the remote doubles as a game controller. The headphones are half-decent quality - use a proprietary plug, but are OK.
There is one lav for 8 people and it is situated far away from the seats so as to not disturb others when going in and out. You get a free little kit of basic amenities (toothbrush, comb etc) in a nice, hang-up type of case like the L.L.Bean kits. You also get some slippers to wear.
Being at the front, first-class passengers get served first. You get a nice linen service, an actual menu, appetizers, choice of entree, dessert, etc. Drinks (including alcohol) are included and they will serve you refreshments before takeoff. As you're right next to the attendant station they will always be around to ask for something.
The trays are larger, plus you have a "side table". At one point I had three drinks plus appetizer plus dinner with room to spare.
The storage in first class is nuts. The attendants take your coat for you and tuck it away, and chances are the only person using the massive overhead bin is you.
(The bin is probably mostly useful since first-class customers get an allowance of two rather large carry-on bags, plus a briefcase/laptop/purse etc. If you check your bags you can expect to have a lot of room up there.)
Your seat is not shared with anyone, so you can pop out anytime and grab something without disturbing a soul. Oddly enough, the seats have no pocket in front, so this can be important. There is actually no place to tuck your bag and it needs to go up above. You can naturally bring it down anytime - you have enough space ahead of you - but larger bags may prevent the seat from folding flat.
You'll also find you don't know what to do with your laptop, two pillows and blanket until you figure the storage options out. There's quite not enough floor/shelf space plus you again have no pocket. Most people make do with placing unimportant items on the floor in front of them.
Anyway, your side table pops open and can hold tons of stuff, plus you have another smaller pocket on the other side and a little cupboard for items like books and phones. No way you can run out of space, and you'll find yourself spending a lot of time moving stuff around.
To my mind, the food was very good and the service was too. I suppose frequent flyers and older folk can snob all they want for other airlines or the "good old days" when they served caviar, but I'm not so spoiled as all that (yet).
The seat does fold flat, is about 6'3" long extended, and is reasonably wide. I'm not a big guy by any stretch, but I found it comfortable enough. Linebackers will complain, I'm sure, though I'm not certain there is any reasonable solution for the very big & tall.
Even when "flat" the seat is not perfectly flat. It's a hinged chair, not a mattress, after all. But it's plenty comfortable to let you rest after getting up at 5 am to make your flight(s). Helps with adjusting to the time zone differences as well.
In First, they'll add sheets to your "bed" (a turn-down service) if you ask them. I didn't ask as I didn't even realize what that service was until afterwards. I suppose it might make the seat more "bed-like", but I kind of doubt it makes a significant comfort difference. I suppose it may if it includes a heavy blanket or pillowed liner or some such.
After a few hours you can develop a sore spot on an arm or elbow where it presses into the hard sides of the "bed". But when turbulence hits it's kind of nice to be lying down inside your little cocoon. You get shaken around a bit but it's not so bad lying down, for some reason. I found it kind of fun and not at all disturbing.
The footwell is directly in line with the seat and is pretty wide, making it easy to get comfy. It's padded and extends the bed another few inches when the seat is flat, becoming part of the bed itself. It is way too far away to serve as a footrest unless you are especially tall, but since your regular seat includes a proper footrest this isn't an issue. This footrest isn't quite big enough to qualify as a shelf except for the smallest items.
OK, so that's first. Is it worth the upgrade from BusinessFirst? What's the difference?
In BusinessFirst, you still have your pod-seat-bed, but they are built in tandem, side-by-side, two seats to a unit.
This means a few things. First, you are not as separated from your neighbors. Second, you share both armrests - one is wide, the other is narrow. You lose all your storage space - sacrificed in the name of making the seats four-across.
And you may find yourself having to step over your neighbors bed to get to your bags in the overhead bin. This happened to me for a few hours, and it took a while before the path cleared to get to the lav.
The factors above are what most people piss about when they talk United business class. Their shock and horror at sharing an armrest is a terrible thing to behold. I gather other airlines have different business class seating, but I have no experience with them.
The lavs are next to the business class seating, and their lights are on even when the main lights are out. So every time the lav door opens, the light and noise might bother you. For some reason the one near me had a terrible hissing sound, probably from the vacuum-operated sink or loo. Pick a seat away from the lavs if you can.
The seats are a few inches narrower and shorter than First. Not a big deal unless you already know the difference. While in First I could sleep on my back, in Business I had to sleep on my side, which required a bit more tossing and turning. Still got a little sore spot from the hard sides, but nothing to fret over.
The side-by-side seats also mean narrower footwells, which are canted off to one side rather than being straight-on to the seat. This makes it a little harder to get comfy. I don't know why they did that - it's odd, it's unnecessary, and it doesn't save any space or cost in the tandem podule design, so I'm guessing it was a conscious choice to distinguish business class from first class.
There's also no bedsheet turn-down service for business class, as far as I know. (Boo hoo.)
Despite the side-by-side arrangement, you don't tend to feel your neighbors moving around. You're OK even if they get up or roll over. I imagine the seat padding absorbs most of that - unless maybe you have a seat-slammer who falls into place rather than sits down. My neighbors were nice so nobody had to put up with that. Ambient noise is high enough to not disturb others with snoring.
You get one pillow, which is maybe a blessing since again there's nowhere to put it when you don't need it. You'll end up squidging it around your back before you find the right spot, but you'll be thankful anyway - it seems that United seats, regardless of class, are not made to fit a human spine., so the pillow will be supporting your lower back when you are not sleeping.
Despite this I managed about the same amount of sleep in business as in first. YMMV.
You get the amenities kit, but a little smaller, and a pouch rather than a fold-out case - again, to distinguish the two top fares from each other, I'm sure, and no other reason.
They perch these kits on the TV shelf before takeoff. The shelf is too small, resulting in amenity kits falling off the shelf and littering the floor at takeoff - which is rather funny, actually. I have no idea why they don't put a little fence or mesh net on that shelf to hold stuff in place.
The kits are fine and have nearly as much stuff as the first class ones, and the items "lacking" are nothing most people would use anyway. Maybe a few people (ladies?) out there might find a use for pocket-sized emergency hydrating mist, but I don't.
You still get your slippers and headphones too, though again finding places to put everything is a challenge. Not everything fits in your narrow little footwell and you have little to no storage space to call your own.
The food is the same and so is the service, but you are further away from the attendents so they're not seemingly instantly available all the time. I had no coat outbound so I couldn't say if they take it for you or not, but I suspect not.
It can take significantly longer to get served the initial meal due to volume and the fact that First is first, but likely not nearly as slow as economy class. Drinks and booze are still free and plentiful, though you have fewer spots to place them and so will have to pace yourself. Econo flyers will see nothing to complain about.
The odd thing about business is that some of the seats face in reverse, like on a train. Some people might like that, especially if you're close to the lavs, since the bathroom light won't be shining in your eyes all the time. I didn't try it but I'm told once in flight you can't tell you're facing the tail.
Some people complain in on-line comments that the face-to-face seating forced them to look at their opposite number the whole flight. Besides the obvious fact that the claim is a little silly - people manage it on subways and trains - you do have your TV plus about ten feet of distance between you and your opposite number. I bet you could manage.
And that's about it, really. In first, you get slightly better/faster service, much more privacy, a slightly more comfortable bed/seat and places to put your stuff. Plus a sense of fun being on top of the heap - at least for a little while.
I can say that in both seats I was actually slightly disappointed that the flights were over so soon - and when you're talking 9.5 and 11.5 hour flights, that's saying something. I think I watched more Sapphire and Steel in my hotel room than on the flight, and I never even got to season 1 of Arrow.
These fares are kind of like going to a five (four?)-star restaurant with a an open bar, a big overstuffed lounge chair, free VOD and a bed. What's not to like? It's actually comfortable - dare I say enjoyable? - to fly this way. Have a good meal, drink some drinks, watch a flick and take a snooze. Not shabby at all.
What you're really paying for to upgrade BusinessFirst to First is privacy, storage and convenience. If you have work to do, have critical tasks at journey's end, or pack your entire damn office into your two carry-ons plus laptop bag, this might be worth it.
For the rest of us, it's a fun splurge (if the price is right) to enjoy the I'm-First experience. And it is fun, or at least I found it so.
Unfortunately, being an ordinary Joe, I can't afford a $7k ticket anywhere when a $1k ticket is available. So this is likely my first and last experience with First or Business class.
I can tell you, however, that business class in something like a Canadair 700 regional is a total waste. The seats are still excruciatingly hard and uncomfortable and there is really nothing on offer compared to econo. Two hours anywhere in those jets is two hours in purgatory. Don't bother upgrading.
My advice: if you have a long overseas flight, a (rare) business-class ticket and the upgrade price is *merely* setting your teeth on edge - rather than breaking the bank - upgrade yourself to First on your outbound flight. Life is short. It's worth it once.
Disclaimer: I have nothing to do with United except having to fly with them every now and again. Unfortunately, they seem to always be least expensive, in my neck of the woods anyway.