Agreed with Columbo. If size and/or weight is important, then m43 cameras win out by a country mile. Not only are there actually small and light cameras and lenses, there is a complete lens line up top to bottom, prime and zoom, telephoto to ultra wides, pro performance and plastic fantastic. You also have manufactures (Olympus and Panasonic) making lenses for the same system, so often times you have a choice between manufacturers. And the m43 mount is an open standard so althugh 3rd parties haven't put a ton of effort in the AF, metering and all electronic stuff works perfectly.
The sensors are very good (Sony), so the cameras tend to perform as well as Canon APS-C cameras.