I recently picked up a 6" GP 100 I was deciding between a 4.2" and 6"
My uses were similar.
1. Range use (I knew I would not be everyday carrying either model)
2. Possible woods carry
3. I reload so I wanted a 357 to try out some recipes for.
4. I wanted my first revolver to be a tank.
Why I liked the 4.2 better:
1. I thought it looked better (in pictures)
2. I felt it would "Point" better at the range with a shorter barrel - also faster switching between targets
Why I liked the 6" better:
1. It had a longer sight radius
2. Longer barrel meant higher velocities with the same ammo (in 357, velocity is king)
3. In WI I could hunt with a gun with a barrel longer than 5.5" (not my original intent but now that I can, I may)
I went with a 6" because the pros for my uses outweighed the con's. There's also something about the 6" 357 that just feels right... In person, the 6 didn't look as bad to me as I originally thought from the pictures online As far as pointing and balance of the two guns once I got to hold them, there wasn't much difference to me in that regard either. The 6" is 5oz heavier than the 4.2 while that's on the "wrong" end of the gun, neither the 4 or 6 are lightweights in any regard, and weight on the end will help with those stout 357 loads I plan to shoot... The velocity increase was also a pretty big plus for me too.
I do have a holster for it, and think that it would be fine walking around a camp. Its a bit hard with a 6" barrel to sit in a car, a truck or more upright vehicle might not be bad... Either way, if you're thinking youre getting a 4.2 GP (or even a 3") for EDC, you're fooling yourself. My vote would still be a 6, especially if your going to be going to the range with it 75% of the time or more.
I'll echo what was said from the poster above me, if you plan to shoot a variety, get adjustable sights... I still wonder why the "Match Champion" is the model with the fixed sights...