RE: Which would you rather build on?
I built my work bench out of a 4' x 8' sheet of 3/4 plywood. Then layed a 4' x 8' piece of 1' foam on top of it, it is a very dense foam. And for my wings I use the GP building board, thats what seems to work for me. I am on my third kit and havent had any problems with my set up yet. Like others have said it boils down to personal preference and just making sure everything is flat and level.
john