I think your chubby Dex has more personality, but it may just be the angle of his head and that surly slouch he's got goin' on.
One thing that jumps out at me; his right fist moves in front of his face for one frame in both versions of the run cycle, and it looks a bit like he's punching himself in the nose. Try extending the arm a little farther forward in the chubby version, or in the thin version you could just slide the head back a bit and that would fix the leaning problem at the same time.
Something else that's bugging me just a little is the Squire helmet. It seems like it sits a bit too far forward on the head. It's clear if you look at his silhouette...
"I am not an animal!"His hair already leans to the front so with the helmet sitting on top it makes his head look unbalanced. Here's a quick edit:
Make sure your helmet fits snugly and securely. Safety first!There, I think he looks a bit more comfortable now. Remember that a helmet sits on top of the skull, not on top of the hair! Also I might just be misinterpreting the shape of the helmet but the little "ear" thing on the side looks like it should be covering his actual ear. I didn't bother putting that in my edit though, since it's more of a stylistic thing.
Keep it up!