Wetsuits are just large swamp coolers on the surface, you need to get it off as soon as possible once out of the water or you will never get warm.
I own and dive both wet and dry suits and I have to say I much prefer diving wet. Even a very good fitting dry suit is not nearly as streamlined as a wet suit. I normally use a one piece semi dry with a vest/hood combination. This offers good flexibility and less bulk than a farmer john with better warmth and I stay warm with bottom temps in the upper 30's.
Dry suits involve more task loading in some circumstances as with doubles you end up having to manage the air in the suit as well as in the wing. The drysuit also is generally bulkier and has much more drag which takes much of the glide out of each kick. PLus, even with snug fitting legs on my suit I still have to be concious of the potential to get air in the feet and this limits the attitudes you can comfortably achieve with a drysuit. No head down verticle descents or standign on your head while poking around in a crack or fissure with a drysuit.
What prompts the move to and from the drysuit each year are the temps above the thermoclines. When I start getting cold during the deco stops, it's time to switch. It is the period of time where I switch from a wet suit to a dry suit that I hate the most as the disadvantages of the drysuit are the most obvious after a season with the last 100 or so dives in a semi-dry. By late spring, I have consigned my self to the limitations of dry suit and developed an appreciation for the warmth it provides in 32-35 degree water, but I still look forward each year to water temps warm enough to put the semi-dry back on.
I suppose it's like monogamy. If I dove a drysuit to the exclusion of all else, I'd probably be happier and spend my days exclaiming how great dry suits are like most other drysuit divers. But that is not the case.
Pesonally, if you are staying warm in the water, I'd think long and hard before switching to a drysuit. Despite it's warmth advantages, and a popular opinion that drysuit divers are more advanced, more affluent, or ooze more general coolness on the dive boat, drysuit use comes with some significant disavantages.
