Having used both EPM2 + EOS-M, here are my comparisons, some of it subjective:
I would think the EPM2 + 17/2.8 might be just a touch more money than the M kit. Maybe by like $50.
The would be very comparatively sized. The EPM2 + bundled flash might be a hair smaller than the M with it's bundled flash.
The EPM2 would be faster to shoot with. The ISO of each is very close. DR is pretty close in my practical experience when pulling highlights back in RAW, though the EPM2 rates as a bit higher.
Olympus PEN E-PM2 vs Canon EOS M vs DXO Mark gives the EPM2 1 stop of DR over the Canon at ISO 200 and 400, and says they are about equal after ISO800, though the EOS-M has an ISO100, with the same DR as ISO200.
I prefer the 22mm lens over the 17/2.8 or the 17/1.8. Bokeh, color, etc. I really like this 22.
I find I can get color from the EOS-M that I prefer over what I could get from the EPM2 (I found I had to work both in post). I can saturate colors, and brighten and darken images more easily without hue shifts on the EOS-M.
If you are happy with the EPM2 + 17/2.8, then it's not likely worth the change. The EOS-M does get you 1 stop faster with the 22/2, ISO100 and maybe just a bit more shallower DOF if desired. For me, it was about 2 things: trying something different after 4 years with m43, and the 22mm lens.
Just MO.