I have the Sherwood Kinesis EX and have been happy with them. If you are looking for maximum power the stiffer the fin the better all other things being the same. So to evaluate your selection: Sherwood Kinesis EX(the black version) is the stiffest. Sherwood Kinesis as you stated is stiffer than the Mares Volo Power. I`ll add another similar design for you as a bit less stiff the Sherwood Spinta also uses the pivot point design and is even less expensive.