I own a S&W 15-22, and just this Sunday, got to shoot the Sig 522 at the range. The Sig is significantly heavier. As in, if you like to put down lots of rounds, this will become a factor. I've never had any issues with my S&W feeding. Sounds like the Sig does (according to chinalfr). I will say the guy who let me shoot his 522 was using bulk stuff too. I use the federal milk crate bulk stuff with my S&W, NEVER EVER an issue.
With that said, if you're into all metal, heavy, solid, go Sig. They make great guns. I just donno that it's necessary on a .22 plinker. Furthermore, if by any chance you can shoot both, I'm sure you'll decide for yourself really quickly.