OK, I'll start the rumor... I heard of extractor issue with the M&P, so it's a no brainer...
Either is a fine choice, and both are American made. Which makes either an even better fine choice in my opinion.
You could ask yourself a couple of questions to help decide. Do you want/need safeties?. The Ruger's all come with safeties, The M&P, either way (although I don't believe you can have a manual safety and a mag safety on the same gun, least I recall they don't offer a model with both). Both are super easy take down. The Ruger comes with a reversable back strap, while the M&P comes with replacable wrap around straps (not all the way around).
I have one of each in the 9c, Both have been 100% reliable, but I tend to favor the Ruger when just target shooting.
Don't know about your area, but you can probably find the Ruger for about a 100 cheaper than a S&W, if that matters. 100 bucks can buy a lot of ammo, or some ammo and a good holster.