Gnome, I think, though I'm not an expert.
You get to make Battle Chickens, you get the mind control cap, and you get the death ray. Death ray is ranged, but can hit for > 1k, especially if it crits.
Goblins get a land mine (which takes a while to activate once you place it), boots that duplicate Sprint, but can blow up, and a couple other things.
From just about everything I've heard in general, gnomish is the way to go. However, I have never had a L60 with engineering, so take what I say on the subject with a grain of salt, and do some research with people who've played with both.
-Arlos