The best advice I can give you is to find fins that fit well and are comfortable on your feet. The rest will take care of itself. And trust me when I tell you that you don't have to spend a lot of money to get a good fin that will serve you well.
Split vs Paddle - I don't think it matters all that much for normal recreational diving. I'd dare say if you tried on the top 20 fins that are sold today and dove with all of them, the difference you would notice would be minimal.
Don't get caught up in the "one is faster" or "more powerful" than the other. Guess what. Diving is not about power and speed. You'll never find yourself in a race when you're doing a dive. As a matter of fact you want to do just the opposite. Take it nice and slow. Look around and see it all and you don't have to swim far or fast to do that.
Also, don't get caught up in all the great marketing hype you'll see about fins. Some will claim their fin most closely resembles the fin of a fish. Big deal! We ain't fish. Our body is nothing like that of a fish, whale, or dolphin. We don't and never will swim like them. (But they'll never walk around on land like us.) And there are so many cool names now for fins. Like:
Atomics: They have one called, "Smoke on the Water." (Wow. That's gotta be one heck of a fin to be called that.)
Mares: They have names like "Volo Power" & "Raptor" (Make sure some large bird doesn't carry you off with those.)
Scubapro: If you don't like the "Twin Jet" you can step up to the "Twin Jet Max". (Jets........gotta be really fast to be called Jets)
Aqua Lung: They have a new one called the "Slingshot" with "Power Bands". (All I can say is hold on to your reg and mask cause they may get ripped off when you are powered through the water with your first couple of kicks.)
Apollo: They have the "Bio-Fin Pro" and "Bio-Fin Pro XT" (I think you have to dive as a profession to have anything called Pro)
Force Fins: They have the "Tan Delta Force Fin" (If you get those and get in trouble Chuck Norris will save you) and use terms like "Vortex Generators" to describe their fins. (Sounds like something James Bond needs to blow up to save us all)
Now don't get me wrong, all of these are great fins. All would serve you well. But many of these are fairly expensive fins. I have dove all but the Apollo fins and guess what I like just as well, has performed just as well, and I bought them for less than $70. They are the Mares Avanti Superchannel Full Foot Fins. (Cool name also) I've used them in stiff currents in Cozumel and they did just fine. I've had them in no current conditions in the Caymans and Bonaire and they were flawless. And not once have I had to race anyone or power my way out of some dangerous condition.
The bottom line is don't worry too much which fin is best because no fin is best. While they may look a little different, they all have the same function and that is to move you through the water and they all do that about as equally as well. Save some money on your fins and put it toward a really great fitting BC or wetsuit. Now that will make a difference in your diving!