686+ Reconsider Buying New.
I'm not going to say anything bad about the Ruger. I've never owned a GP100, but that's just a matter of timing. My several other Rugers are liked every bit as much as my several S&Ws.
My 686+ was bought gently used for $400 a few years ago. The guy that sold it to me was switching to autos, and gave it up after shooting maybe a dozen boxes of ammo. I got the box, warranty card, and oh, too bad, no Hillary Hole. I won't buy a new S&W while they insist on putting a LOCK in the design. My old Model 28 and Model 19 still kick hind end, too, and neither one of them were bought new - gently used.
I've been shooting handguns for 45 years now, and there are LOTS of really good used handguns at gun shows. Larger calibers tend to get used less than, say, .38s, because of cost of ammo and blast. Yes, SOME of us send half a ton of lead downrange each year in some of our favorites, but most people don't do that. You can still get a fine slightly used revolver for under $500, just take somebody with you who's good at picking them. You'd do the same if you were buying a used truck, right? If you're really not good at looking a used handgun over, drag a buddy along, no shame in that.
And oh yes - Rugers are even harder to wear out than S&Ws or Colts, so if you find that barely used GP100, snap it up....