I was looking for a 686 and then gave up. My brother has 2 plusses: a 4" and a 2". They are 7 shots and really nice guns. I found a GP100 4 inch from one of the partners here. I had it shipped to a local shop and I'm now waiting. If yu have access to a 686 or 686+, jump on it. The research I did revealed that the GP100 is a solid revolver. I don't think I'll be disappointed.
The S&W 686 was designed from the ground up to handle .357 pressures as well as be in a size for competition and general carry. A compalint about the K-frame Smiths in .357 was that after a steady diet of full bore .357's they started to "shoot loose" Although the K and the L frames have the same grip there is more metal around the cylinder and the area of the forcing cone is beefed up. The actions of both the K and L frames are the same so you can get a very nice double action set up on either one. The GP 100's are extremely serviceable and over built to a fault. You will be hard pressed to do any 'damage' to these Rugers. But IMHO the S&W has a better action.