I could argue in circles .. depends on what I'm using it for.
Averaging things out, I think a 4" L frame or GP100 would be hard to beat. There are better guns for specific purposes but looking across the board, I'm not sure they can be beat.
My favorite carry .357 is a S&W pre-lock J frame with a 3" barrel and adjustable sights. Vicious bitch to shoot, nice to carry. For hunting, I'm fond of the 8-3/8" L frames and 8" Python. I like the GP100 6", but the 160 / half-lug version, not the 161 / full lug version. I wish Ruger would offer a run of 8" GP100s with the barrel-mounted rings. (Is Lipsey's listening? :)) I'm a single action fan. Practically speaking, the 6-1/2" SS blackhawk is probably king but for sheer class, a 4-3/4" barreled Colt SAA would be pretty fine.
Of what's currently available, I suppose I'd lean towards the GP100 Match Champion with adjustable sights and swap the grips for a smooth compact grip.
