EOS m3 lens will be quite abit bigger or not as large range.
i own a G1x mk2 and i think the downsides are:
wifi is useless
too many customisations for front ring and back ring and dials but some key ones are missing.
wide end max aperture is uselessly soft even my samsung note 2 does better sharpness.....
dynamic range is very good for compact, but not quite DSLR level.
other that that, very nice colour, once step down in aperture, very very scarily sharp. very good macro mode too.
i would only recommend to advanced user.... not very point-and-shoot DC.