If I could only have one, and were allowed to use it as a carry gun, as well as hunting/home defense, I'd go with the GP100 4".
I've slicked mine up and the trigger feels very nice. I like it.
In .357mag, I also have a 586, a Ruger Blackhawk and a Colt Model 3 5 7.
The GP100 isn't as precise as the 586 or Colt, but I just like it better. I am able to hit what I want with less concentration on the hold/mechanics. I can get better results with the other two, but it takes more deliberate effort on my part.
From a long term accuracy and reliability point of view, the GP100 would be the one I'd keep.
However, in California, where carry is hard to be able to do, I may as well keep a Blackhawk .357/9mm convertible- so that I have ammo options.
The 586 is MUCH more elegantly made and feels smoother, but I am better with the GP100.
The Colt 3 5 7 is even better than the 586, but- again, I am better with the GP100.