Yeah, I knew the 6 mil would be overkill for down here, but I also surf in Maine from time to time (and might move there), so I was trying to make the best decision based on not wanting to buy a brand new winter suit if I do move. You're right on the 4/3, though. I just need to update my 3/2 -- it's a super crusty Hurley that has seen too many sessions.
I say 3 suits and a top. 4/3, 6/5/4, and spring suit, plus a short sleeve top. That is what I own and loved having the 6/5/4 in the winter. I would be sweating when the water and air is in the 30s and the 4/3 is good the rest of the time with the spring suit for late Spring and Fall, plus the top for summer.
I lived on Delmarva for several years and would rather be hot than cold.
im in maine and im in a 2 yr old 5/4 and its no prob..and im plenty skeeny. the 6/5/4 excel is a hundred bucks cheaper that the 5/4 drylock though so do the math. and buy your suits in NH and save on tax. i mean i moved here from san diego.. if its cold its cold why split hairs
and if you do move here be prepared to say bye bye to those punchy beach break barrels.
4/3 Full (w/ a hooded poly-vest inside)
If you are really serious about staying in the water for longer than 2 hours in the dead of winter, you'll probably want a 5/4 to last on those really cold Jan/Feb days.
You can get away with a good hooded 4/3 like a Drylock and a heated wetsuit vest too, if you wanted to keep the rubber thin but stay warm. You've got two options on that route:
Quiksilver Cypher Vest
Thermalution Heated Wetsuit Vest
Vasoline and Whiskey!