This was a quick test only, using a popular torrent client.
The Netgear is a recent (faster) example running the latest DD-WRT. The pfsense box is an eBay i7-7500U special with the latest pfsense.
Speeds are peak speeds through Private Internet Acccess (PIA) using AES-256 / SHA256 on their "Next Gen" network. There were no changes to the rest of the setup between the two trials.
- Netgear: 4 MiB/s
- i7-7500U: 38 MiB/s
That's almost a 10x improvement.
Note I couldn't get these speeds using all torrents, as some of the sources are limited.
However, I know that the Netgear can't exceed 5 MiB/s no matter what, while the i7 definitely can do 38 MiB/s. It's possible the i7 might be able to go even faster.
From this, it does appear obvious that the Netgear is quite limited with respect to VPN crypto.
Obviously the i7 is vast overkill. I got it since the price difference between the i3 and i5 was nominal and I really only feel like doing this once. See here for tips on buying such a box.