Size and weight
One BIG advantage of the Micro Four Thirds system is, of course, the lighter weight. Some have also questioned the Pro lenses being large and heavy when the whole idea of the system was to be small and light. My feeling is, everything is relative and you need to compare like for like. With the cameras side by side, it is immediately noticeable how much smaller the Olympus is than the Canon 7D Mark II, with a difference of approximately 500g. Against the Canon EF 100- 400mm f/4.5-5.6L IS II USM, the Olympus M. Zuiko Digital ED 300mm f/4 IS Pro looks similar in stature, but has a weight saving of approximately 400g. Swap the 100- 400mm to a Canon EF 400mm f/4L DO IS II USM, which is the equivalent in APS- C terms, for a direct comparison and the difference is about 1.2kg.
It’s not all about pro lenses, either. For relatively modest sums, the micro system has some very nice quality lightweight lenses. I use the cheaper Olympus M. Zuiko Digital ED 9-18mm f/4-5.6 wideangle, which is incredibly petite, but not short on quality, along with a Samyang 7.5mm fish- eye, a 25mm Panasonic/Leica H-X025e Dg Summilux and an M. Zuiko 60mm f/2.8 Macro Digital ED. All of these add up to less than 1kg.
The Canon 7D Mark II and EF 100-400mm vs OM-D E-M1 Mark II and M.Zuiko 300mm