I use scubapro Jetfins (the original black ones) for diving with boots (cold water/drysuit). i highly recommend getting spring straps for them - much easier to put on/remove, and you don't have to worry about them breaking. You can also take the replacement straps from Twinjets and put them on jetfins for a quick release option. These are the fin of choice for many cave divers/technical divers because of their ideal combination of size and thrust - plus, if they're good enough for Navy SEALs, they'll probably work for me. They last forever also - I'm using my dad's original pair, which are roughly 20 years old. For warm water I use Mares Quattro Power full foot fins - great power (as good as most freediving fins) and nice size. The Mares Tre full foot is a good alternative for smaller individuals/weaker legs (I am 6ft/185lbs and a freediver - smaller people have trouble kicking the quattros due to their size).
Split fins are not very effective for small movements - they are a great fin if you have bad knees/ankles, but are not ideal for many situations (as highlighted by some others). If you're pushing a big camera rig, you won't move very well with them. The same goes for diving in current - they're almost useless. If you dive in these conditions and need ot hold your position for shooting, split fins are not what you want.
Or technisub Alas, been looking for those, too.
The Alas are a great fin, but they're not manufactured anymore (due to dioxin emissions, i think - some chemical byproduct got the process shut down). You can still find them occasionally, but they're usually had to come by for less than about $225 anymore - they're an extremely popular fin for underwater hockey/underwater rugby, so I keep my eyes out for them, but it's rare when a pair shows up.
Does anyone have any experience though of Force Fins? I have a couple of mates (not photographers) who swear by them even though they look really weird - and they are expensive too.
I have never liked the force fins - they're not very good in heavy current. They perform a lot like split fins (although slightly better, i think) but not as well as other fins. That being said, they are one of the fins used by the US Navy SEAL program (alongside Jetfins) - I was told this is because of their compact size, but based on my personal expirience with them, i'm guessing some admiral has a brother who owns the Force Fin company.
These are basically my observations from working on dive boats - I've seen a lot of fins on a lot of people, with significant diving in current - the split fins just do not perform as well in general diving conditions as traditional designs.