It's all in what you can afford to spend. A six-shot 4" 686, SKU 164222 & 39.7 oz, has an MSRP of $829 - think $670 at a shop that likes your business. The Ruger GP100 4" in SS, KGP-141 & 40.0 oz, has an MSRP of $759 - think $600 at a shop where your patronage is appreciated. The GP100 is often heralded as being 'built like a tank' and heavier. Here, both being full lugged, it is heavier - by .3 oz. It is constructed of cast steel - Ruger has patents on their use of cast metals. The S&W is hammer-forged and heat treated - and rated for full SAAMI-spec'ed .357 Magnums. I started my revolver life with Rugers - I now have all S&Ws. The S&W is worth the extra money... as is their lifetime warranty, which is accessible via a toll-free call.
If money really isn't the determining factor, consider the 7-shot 686+, SKU 164194 & 38.9 oz, MSRP $849 ($685). My one 686 is a 7-shooter + model, actually a 5" half lug 'Stocking Dealer Exclusive' from some eight years ago. I have no trouble reloading with my four HKS #587 Speedloaders - even in the dark. That extra round may be important! In fact, I think an 8-banger is even better yet... consider the slightly larger N-frame 627 Pro, a 4"-er, SKU 178014 & 41.2 oz, MSRP $969 ($800). It comes with a lot of extras - including an enhanced trigger, moonclip ready, and easily changed front sights. Well worth the MSRP difference of $140 over the sixshooter 4" 686!
If you like the .45 ACP, a 625 Pro (625JM), SKU 160936 & 40.3 oz, MSRP $979 ($810), is a great revolver to have. Even though it's the same approximate mass as a decent 1911, the recoil is greater - there is no action to absorb some recoil energy. Shot indoors, the big boom of a .45 is less damaging to your ears than the supersonic crack of a .357 Magnum. Ammo is about the same cost, too. Here are my 627 & 625 Pro models.
A plus for the 625 .45 ACP revolver: It really is a 'big-bore' revolver with a frugal diet and recoil, not to mention that it, with moonclipped ball ammo, reloads faster than any other revolver/caliber!
Good luck with your choice!
Stainz