P. Suttonorum (BES) clearly has spikes on their sides, no matter the size is. Their eyes are also less blue and got bulkier looks. Body colors are also tad dark grey-ish. You may need to see them both in person to notice they are two different species.
For which one is more desirable, dunno. BES may be harder to acquire at the moment but some preferred P. Cochliodon (BEC) over BES due to their bright blue eyes and jet black color. BES is also got (bad) reputation for being pleco tankmate killer.
The reason why they're expensive right now is due to not showing up for so long, you need to buy one at monster size (14"+) while you can get smaller BEC which cost less and look almost exactly the same.
It's up to fish keeper's preference IMO.