I'm actually selling the M11 as I got an M11X last year, and can't really justify having the two. TBH they are really as good as each other. I like the fact yo can change modules in the M11, but I like the fact the M11X takes a couple less batteries. The M11X is also a little faster than the M11, but I'm no Lee Martin so it doesn't really make much difference to me, I may be crash a little faster
The 11X also has a few extra features, but nothing I'd ever use.