I currently have a 4" 629 that I like and shoots well but I haven't compared a lot of different loads.
I've tried the Mtn gun (w/ tapered barrel) and the full lug classic but my current half-lug, non-tapered standard is what I prefer. The weight diff between it and the mtn. is insignificant for my use. Whereas the full lug seems muzzle heavy to me.