dfx
Contributor
No, the best warmth would be a dry dry suit, because air is a good insulator and water isn't. However, when you're comparing wet suits, then you're correct: thicker neoprene = better; less water exchange = better. That's all there is to it, at least when it comes to the long term.By that theory, the best warmth should be a flooded neoprene dry suit, by virtue of the fact that water EXCHANGE in a dry suit with a small hole in it is minimal, and the suit still has insulating capacity.
Unless you're talking a completely flooded dry suit, this is an entirely different matter. Water evaporates in air and consumes heat when doing so. It makes you cold and will continue doing so until all water is evaporated (which, with a leak, will never happen).But I can tell you that being wet in a dry suit is nowhere near as warm as being dry in a dry suit, having had significant experience with both states.
With a completely flooded dry suit, it's only a matter of (uncomfortable) time until your body managed to warm up the water inside the suit. Afterwards (if you manage to survive that, as water takes an enormous amount of energy to warm up) it should be comfortably warm.