The Ruger GP100 and the Smith 686 are both so good that there are endless threads about which is "better." Our family owns two GP100s, two S&W 686+s, a Smith 327PC (8-shooter) and a venerable 1980s version Dan Wesson .357. As you can see, we like .357 revolvers.
My thoughts:
1. Forget all this internet chatter about the Smith lock. It is irrelevant. No one uses the darned thing and it does no harm.
2. Ruger really got everything right with the GP100. Now and then a company does this and really puts out a great product. That is the GP100.
3. The 686+ is just a great revolver; just what you would expect from S&W. The SA trigger feel on the 686 is beyond compare.
4. The Ruger and the Smith have "different" DA pulls. Which is better? It depends what you like. I will say that I had a trigger job done on my GP100 and it now has the best DA trigger of any revolver I've ever shot. My 686+ trigger was stiff out of the box but like most or all Smith triggers it is mellowing nicely with use.
My $.015.