First, we should compare the facts on similar 6-shot .357 Magnum chambered 6" barrel Ruger GP-100 vs S&W 686 - from their websites.
Model Stock # Weight MSRP
GP-100 1707 45 oz $779
686 164224 44.9 oz $819
Where is the 'massive' difference in mass? 0.1 oz isn't much. Additionally, Rugers are cast steel, while S&W's are hammer-forged and heat-treated. Both are SAAMI rated for .357 Magnums and both take the same HKS Speedloader (#586A). I quit buying Rugers over a decade ago due to their sloppy machining and finishing, not to mention their poor internal QC. They have improved since then - no doubt. Still, my DA revolvers (SRH, RH, & SP-101) and myriad of SA revolvers, from SS-SBH, were all delivered new as 'works in action'... the .45 Colt RH had to go back to have another new cylinder, pawl, hammer, trigger, and springs fitted. I did get it back within a month. I own fewer S&W's - but love everyone of them. One, a 351PD 7-shot .22 WMR, had a bad extractor - it would leave two rounds every cylinder full. I had it back in a few weeks - and the calls, s&h, etc, were on them, too - a welcome change from some makers.
I don't believe in 'over' charging my homebrew ammo, so the question of which one is more stout has no meaning to me. IF I need 'hotter' ammo, I go to a hotter caliber. Oddly, my still fondest memories of a Ruger are of my 7.5" .454 Casull SRH. I no longer have the need for so much muzzle energy, however. If I had not 'discovered' S&W revolvers 9/02, when my wife bought me my first S&W, a new 4" 625MG in .45 Colt, I likely would have remained a Ruger guy. She started my S&W-lust, so blame her - I will continue to thank her, however!
If you want a great .357M x8 shooter - try out the 4" 627 Pro, see below. It's a bit larger - an N-frame - and has a spring-loaded front sight, easily changed without tools. Mine is a close second to my 2 5/8" PC627 UDR, also below.
View attachment 723842
Stainz