For functionality, either is great, although in some cases Rugers may take a bit more extreme abuse (not enough difference to matter to most). Rugers absolutely have me won over with the Blackhawk series for vintage style and durability, especially if you want .45 Colt.
In terms of sex appeal and future resale value for most models, I have no doubt S&W wins hands down. You'll never see a mainline production Ruger having the kind of cache that old Smiths have. But since Rugers have less resale value, you end up getting lots of bang for the buck.
Mauser Werke, Schmidt-Rubin, Colt, Walther, HK, Weatherby, Browning, Ruger, Beretta, Savage, Bushmaster, Marlin, Mossberg, Saiga, S&W, Sig Sauer....a few friends of mine