Well, I haven't done any drysuit diving but I have done a lot of regular tank diving.
A lot of it I think comes down to the conditions in which you will be diving, kicks you need to use, your general fitness, and your air consumption.
If you are fighting currents, need a little cardiovascular work, or struggle with air consumption (normally not a big issue with a background in freediving, but can be if you are built like a tank) I would suggest a pair of split fins. They are more efficient at generating forward thrust, easier on your legs if you have to swim in strong currents, and can significantly cut down on air suckage if you find yourself being an airhog. They are good for situations where you will not find yourself entagled and/or in an overhead or penetration diving situation. Great for a steady flutter kick or basic dolphin, etc. They lack siderails and large surface area for controlled sculling, and thus force a diver to utilize breath/bc for bouyancy control. This is not a bad thing though, unless you are swimming near the bottom with a new diver. In addition, I have yet to meet any diver that can swim backwards in a pair of splits.
Traditional paddle fins like the jetfin or avanti quattro are good for hard turns, and I have found them excellent for sculling or frog kicks. They are definitely harder on the ole legs and feet, and lack the efficiency of a split, but this niche can not be underestimated imho. If you need to manuver in a tight space like a wreck, cave, or kelp forrest paddles are the way to go. The ability to turn in place or swim backwards can be invaluable, especially if you need to be sure not to touch anything and muck the place up. They can be rough if you need to swim in a current, and will exacerbate any air utilization problems you may have.
I have to agree with Jon on the springs. For drysuit diving where the boots are thick enough and heavy gloves are a must, don't mess with anyones "patented buckling system" and just buy a spring.
For Splits - Apollo yellow and atomics have consistantly gotten the best Rodales scores for both ergonomics and objective measurement tests.
For Paddles - I haven't used a Jetfin, but it's almost cultish prevalence among drysuit divers and tech divers either means that it's very good, a solid black color, or both. I love the Mares Quattro. It's a solid fin, tried and true, with a longer blad than normal, excellent handling and sculling characteristics due partially to the rails. The old and new Aqualung Blades are a great paddle fin as well and an excellent choice.
Personally I would by both types as I think they both have thier uses, and I REALLY like having backup in case of fin faliure or you lose one after the first dive in rough seas, etc. Personally I would check ebay at this time of year as there are a lot of people normally selling lightly used dive gear. I just bought a pair of the Aqualung Blades for $5.50 which isn't a bad price at all