For the most part they'll be similar.
A lot of the price goes into fit and finish, and the little upgrades, like night sights and the like.
I picked up a GI model from Rock Island Armory, I've never had any issues other than with some bad hand loads. (Hard to be consistent with a mallet << >>) I'd recommend a model with better sights though, the GI style are hard to use in low light.