I was in the pool today (all my dive buddies are out doing their own thing) and saw a pair of twin jets laying around. I strapped them on just to see what I could and couldn't do with them.
First of all, in comparison to jetfins, twin jets make you feel as if you don't even have fins on. Frog kick with them on seems to be okay but a little sluggish at first. To my surprise, back kicks are completely doable with twin jets. Again, a little sluggish and sloppy in comparison to jetfins but completely doable. Helicopter turns are also doable but far sloppier when compared to jetfins.
Overall, I would say that I was completely shocked with what I was able to do with those twin jets. Would I trade in my jetfins? No way. But certainly, I would encourage the "personal preference" divers to try to learn how to do alternative propulsion techniques in their split fins. My guess is that most will be able to do some measure of back kicks and helicopters with a little practice. It might not be adequate for diving overhead environments but completely usable in recreational environments.