The dealbreaker for me about the SL1 is the lack of AFMA. To take advantange of fast glass, it needs AFMA. Sure, you can use slower lenses, but then it's not much over the EF-M's 18-55...
Really? AFMA missing is a deal breaker? How did you survive before mid 2007 or 2008 when Canon first started offering AFMA? I think when one is shooting an SL1, while it's always nice to have, AFMA is not the primary purpose of the camera. Same could be said for the EOS M. Personally, I think AFMA should be standard on any removable lens camera but it's not a deal breaker on an entry level lightweight Rebel body.
For fast lenses, it is. I had a 20D and a 17-55 f/2.8 back then, and I didn't know how good the lens was until I used it on a 7D and used AFMA. Then I got a 35L, and it was even more crucial to have AFMA. So yes, a lot of my shots with the 20D are slightly OOF. I thought it was the quality of the lens and camera combination. Even without AFMA, it was better than the kits lens, but it was not anything as when it actually got it right. I learned to to take multiple shots hoping to get one whose error was "right on."
And no, the same can't be said of the EOS-M. No mirror, no PDAF, no AFMA issue. And if you're using slower, more compact lenses on the SL1, then the EF-M 18-55 compares well. I got the EOS-M to replace the P&S, and it has done that job well. The 11-22/22/18-55 + M body is compact system. I use the 5DIII much more often, but when DSLRS aren't allowed, I grab the M.