Granted I've never used a dry suit, but I don't understand what difference that would make concerning one's choice of fins. Would someone (maybe smorneau) please explain it to me?
In my case the boots on my drysuit when worn with enough socks for 38 degee water requires a very large foot pocket(XXL). When I travel to warm water for vacation I am often only wearing 3mm boots and usually can get in a pair of standard large fins. Also with a drysuit I need heavy (negative) fins to help keep my feet down when there is air in my drysuit boots. Otherwise I would need ankle weights. Diving in a wetsuit my fins do not need to be negative.