I hate drysuits. Can't stand the gaskets around neck, wrists and ankles. Claustrophobia!
I'm with Chris about windsuit over wetsuit. The wetsuit kind of holds my body together like external muscles and makes me feel like superwoman, protects me from abrasions, gives me extra flotation if I am in the water, and I can wear a lightweight windsuit on the outside of the wetsuit to prevent getting cold from evaporation from the wetsuit.
Actually, I only need a waterproof windjacket on the upper part of my body to keep my torso warm. Legs do not seem to be a problem warmwise. But that's just me.
In cold weather it's super important to keep your head warm -- just as in snow-skiing, and your feet and your torso are next. Again, just my opinion. And in really cold water, fleece-lined booties would be great. Is there such a thing?