Micro Four Thirds versus standard DSLR systems
So if you would like to learn a bit more about the pros and cons of both systems, check out this article
What I want to address is the different lens focal lengths of both, because I've been throwing out numbers like 50mm, 100mm, 28mm, and those aren't accurate standards for four thirds systems.
A Canon APS-H sensor size is more comparable to a 35mm film camera, the standard for film based SLR's. The lens focal lengths for 35mm film systems are more commonly known, so I started there. For instance, a Canon 5d has lens kits most comparable to the old 35mm film system, so its "normal" lens is 50mm.
As you can see, the Four Thirds System has a much smaller sensor and what that means is that the lens focal length counterparts to the standard are shorter (pretty much cut in half)
Standard Focal Lengths (lens types) for a Micro Four Thirds system:
DSLR versus Mirrorless