I'm an old timer and pretty biased, but I'd like to think I've learned a thing or two in my years. I'm also a southerner and spent most of my years in the south (came west about 32 years ago).
The facts are
1) a revolver is aruguably more versatile than an auto.
2) in the eastern US the 357mag will do for almost every purpose
I used the 357 Blackhawk as my primary bush sidearm until I came west.
Of the two choices you posed, I'd opt for the GP without question. The 357 is a superb round and 38s/357s are commonly found everywhere. The 38.357 is easy to load and components and eqipment is easy on the wallet. When I was in college, I reloaded many a cartridge using a Lyman 310 nut cracker loading tool and a powder dipper. Times were tough then and the $$$ were tight.
Frankly, as with the previous poster, I'd prefer the S&W 686, but you can't go wrong with the GP.