Exact reason I got a 10mm Glock 20. Don't really have to worry about it getting dirty. I had dirt, sticks, tree paint, etc all over mine and it fired perfectly. You are going to be shooting them in the noggin when they are charging you(hardest part of body). I wanted the biggest bang in the smallest package. It is a full size gun, but fits my hands perfectly because they are wide/long.
I have one of those OWB kydex holsters that clips to behind where your belt goes, and it is very comfortable to walk with. I used to walk with a Camelback, clipboard, compass dangling, and blaze orange vest with stuff in the pockets and it never bothered me. Always had easy access to gun.
Get both and you won't regret it. Dont even bother looking at anything else.
Eta: I used to typically walk 3-8 miles a day, and had some where I walked 15mi. No problems
This post was edited on 2/6 at 1:17 pm