This is the big debate: drysuit or wetsuit. I say wetsuit all the way. While sailing Lasers, flexibility and mobility are of the highest importance, and the wetsuit is the clear winner in those areas. Wetsuits are cheaper. Wetsuits are also still effective if you get a small tear in the suit, while drysuits are not. All is takes is one area to be compromised, and the drysuit can take in water. Not cool.
I do think it's important to state that all the frostbiting I did was in temperatures above freezing (is that true frostbiting??), so for those of you sailing in truly Arctic conditions, a drysuit might be best. There were days we had to shovel ice and snow off the ramp to launch our boats, and I definitely capsized and got dunked a few times in icy water. I would still choose wetsuit.
My only gripe with a wetsuit is getting it off later is a pain. But that's life. If you want an easy sport go bowling!
This NRS wetsuit was 60 bucks on Ebay, a killer deal compared to new suits from Gill or Rooster. You don't need a Zhik Superwarm, they are stupid expensive and I don't think offer that much of an advantage for the price. This wetsuit also has reinforced knees and seat areas, perfect for Laser sailing. PS if you don't know what a Relief Zipper is, you're gonna love it.