In my experience.......
For a factory gun with no mods I would take the MAC 10 any day of the week and twice on Tuesday, especially PS guns. They just seem to run forever. Brain is a little more forgiving of the M11 than I am. I had an M11--purchased new--that I enjoyed but after about 1,000 rds the gun started to have all sorts of problems, i.e. jams, misfeeds, etc. Sold it, bought two PS MACs and never looked back. Now, there are a lot of modifications that can be done to an M11 to really make it a neat shooting gun, side cocking uppers, task conversions, and new stocks to name a few, but you can do most of these mods to the M10 as well. If you get a good deal on an M11 dont' pass it up, but, for my moeny, I want Powder Springs Ga, stamped on every MAC I own.
BTW: Whether you purchase an M11 or M10 you should get a suppressor to accompany it. Trust me when I tell you that it makes the gun more fun to shoot and hang on to, and the cool factor is way up there. I suggest either AWC MK9, Gemtech MK9K, or Gemtech Viper.
:soapbox