IzzyTahil once bubbled...
I have a pair of Oceanic Vortex splits. I love this fin, alot of power for very little exertion. Yes, I can do frog kicks in them and other modified kicks, no problem. Everything is great, but they suck in strong current. So, my splits are only going to be used for warm and calm water diving. I also have Jets - I find doing modified kicks much easier against the splits but requiring more effort. In cold water drysuit diving I find my jets give me the "stiffness" and propulsion I might need against a current.
Just as a illustration, I was using my splits in 3-4 knot current and I remained "in place" while my buddy, using jets managed to move into the current.
The end result is that I don't use splits in places where the current tend to be pretty stong but will use them in easy diving conditions.