Burleyboy: I have several Smith & Wesson Model 686's in various barrel lengths (2 1/2", 4", 6" and 8 3/8") and LOVE them all!
I have never owned (or wanted to own) a Ruger GP100.
I base this on the lesser aesthetics of the Ruger and the amazing balance, feel, looks, performance of the Model 686's I own.
I am not saying a GP-100 is not a good pistol - I am saying the Smith & Wesson Model 686's ARE outstanding guns and good investments.
Best of luck with whichever you choose - maybe "Daverageguy" is right - consider buying them both?
Hold into the wind
VarmintGuy