Depends on how LONG you're in the water... Fleece and wetsuit are both cold in the drink. Wetsuit warms faster, but when you get out you get the refrigerator effect in the breeze, which makes the wetsuit feel COLDER in the wind. The fleece dries faster, and still maintains some warmth when wet (but not as much as the wetsuit). Wind does cut right through the fleece, so you need some wind protection over it...

The wetsuit does, however, provide less drag when swimming after a sideways cat drifting away at 4 knots!

I prefer the fleece over the wetsuit for range of motion while sailing, as well as it's ability to breathe. It's also easier to don/doff than a wetsuit. If you put wicking undergarments on (rasher), you don't get as clammy underneath as you would with a wetsuit when you get hot.

I think if it got REALLY cold, I'd switch to a drysuit from the fleece/spray combo, and leave out the wetsuit unless I planned on being in the drink a LOT (like surfsailing)

With my current spraysuit/fleece combo, it actually takes a bit of work to get the fleece completely wet, as the harness and spray gear keep the trunk area from too much water intrusion. Last time I dropped in the drink, the full harness and spray gear setup kept my midsection dry for the two minutes it took me to get the boat back up. The legs and arms were soaked, but the spray gear kept the wind off them until they dried a little while later.