The hard plastic "backpacker" fins, which Outcast also sells, actually perform better than their rubber ones. I own both. I wonder if fins that have a longer profile work better than ones that are wider. Perhaps that's why scuba and force fins seem to work so well.
BTW, good thrust from your fins can translate into more trout. I've noticed that, when the fishing is slow, you can often coax a strike if you kick like it's going out of style while constantly stripping and releasing a streamer fly. This is strictly a float tube thing. You need both hands free to pull this off.