[Jon]

If you go with a fin like the Dolphin you will have a tighter fitting footpocket- which means more of your kick will be directed to the fin blade. They are more efficient than the full-foot pocket models and I can swim faster with them. The problem that I have is not being able to wear one like this for more than 15 minutes. My full-foot pocketed fin I can wear for hours and hours.

Another advantage to the full-foot pocket, besides comfort, is that you can wear a thicker sock with it- which may be important for where you are diving. With my Dolphin monofin I could only squeeze a 3mm sock in. With my OMER pocketed fin, or the NEMO fin, I could wear a 5-6mm sock with it. Since you're looking at a 5mm-6mm suit already you might want to consider a monofin with a roomier footpocket so you can put a thicker sock on with it.

Since you have Apollo fins right now you could switch to any pair of long blades freediving fins and see improvements- plus, you could use them for scuba diving. Monofins might be something to move into at a later date?

I would go with the thinner suits and wear a vest. Once you buy a true freediving suit you'll see how much warmer they are compared to a scuba wetsuit.

Jon