I started out with split fins, because the owner of the LDS told me they would be less likely to cause cramps, and I have trouble with arch cramps even when I'm not diving. As far as I can tell, he was right, because I never had any cramps while using the splits. They were comfortable and easy, and I used them right up until I took the class that tried to teach me to frog kick.
When I saw what my fins were doing (these weren't splits, they were softer, long-bladed fins) underwater, I immediately purchased a pair of Jet fins. The next day, I took them in the water, and was sure somebody had strapped concrete blocks to my feet. But I could frog kick instantly. And today, I can frog kick, flutter kick, back kick, and do helicopter turns, and I'm quite used to the Jets. And I have almost never gotten any cramps with them, either.
If you intend to do a great deal of diving, you most likely will eventually want to be able to position yourself precisely in the water. By that, I mean you will want to be able to stop and look at something for some time, which may require that you be able to back up a little, or spin on your axis. You may want to do your descents and ascents while keeping eye contact with your buddy, which again will require precisely positioning in the water, and is immensely easier with the ability to back kick.
You CAN back kick and helicopter kick in split fins, but it is much harder, and I think pretty much requires that you have learned to do it in a stiffer fin first.