I tend to prefer the Whittler to the Stockman, but I do have 3 Stockmans, an older U.S. Schrade mini, a Northwoods med. (Made by Queen, I believe), & a Buck 301 Cadet.
For a working knife, it'd be hard to beat one of the U.S. Bucks (301 & 303), however the other ones mentioned are all great. It mainly depends on how much you want to spend & size.
While my red shield Henckel isn't a Stockman (It's a Whittler), I believe they do make a Stockman & so does Boker (Who, I believe, makes the red shield Henckels).
Sizewise, that's very subjective. Personally, I've found around 3.5" to be ideal, but I'd say between 3.5-4" is very pocketable while still giving you decent blade size.
Good luck.