I had a somewhat different experience with the RX100 - the rather poor corners at wide angle eventually got to me, and the low ISO performance of the RX100 Mk 1 is definitely not up to the same standard as the APS-C sensor of the EOS M - the Sony RAWs are noisier at base ISO. The bokeh from the RX100 lens wasn't great either, occasionally hazy is probably a good way to describe it. So for the types of shots I like to take - low ISO/optimal aperture - the EOS M delivers better output when I have the time to set up the shot. I find the 22mm f/2 to be a very decent lens, other than the CA in the corners (super easy to fix in photoshop), and the extreme corners aren't perfect (but they are pretty good and notably better than my RX100).
The RX100 definitely has the edge in size, AF speed - compared to DSLRs, the AF in the EOS M just feels brutal in certain situations, comparatively, the Sony can't track focus very well, but the one shot AF mode is speedier and more consistent compared to the M. It's about even on ergonomics, the EOS M controls feel a bit more initiative to me (probably because I'm already very familiar with Canon DSLR control schemes), but the RX100 is is much easier to operate with one hand (after you've installed a Richard Franiec grip, that is - Richard's grip is fantastic).
I'd be willing to give the RX100 series another go once Sony updates the lens, but probably not before then. I still like the camera, too - it's likely the best pocketable compact on the market and a great option for many (did I mention it does great 1080P60 video?) - just after an extended audition, I discovered that I'd rather have a better lens than what the Sony offers.
As for the M - it does some things well, but it's a few tweaks (needs a better location for AF-on mapping, better grip, and a second control dial would be nice - maybe something like the G12/G15 implementation) and a great AF system away from being a truly great camera. The IQ is great, and although the native EF-M lens selection is limited, the options that we do have are very good. When I'm using the M I can't help but think how much better it could be with what the dual-pixel AF tech promises to deliver - seriously, give me better AF and I'd be willing to pay big money for a body this small.