Large APS-C (22.3 x 14.9 mm) sensor
Large sensor in Canon M3 ensures a good low light image quality compared to smaller sensor, and it also provide shallow depth of field and a nice blurry background when needed.
Medium size Body
With relatively smaller body compared to DSLRs and better ergonomics compared to Compacts,Canon M3is a good compromise between size and functionality.
Carrying this weight all day may not be very comfortable for you. Body Thickness 44mm
With a thickness of 44mm,Canon M3 is not a pocketable camera for sure.