I am also a slimmer guy - 5'10 165. I own both a snubby and original footprint kit bag - both are great but I use them in different roles. The original has the obvious advantage of holding a bunch more stuff, so I'll use it for camping and longer trips in the woods. However, since my chest is pretty small, my arms will actually brush the sides of the kit bag during vigorous activity (e.g. jogging), so the snubby shines for day hikes and jogs.
Note: I have the original pattern snubby (the smaller one seems to have very limited utility). In it, I can comfortably fit a Glock 19, wallet, cell phone, keys, map, small light, pocketknife.