23fbaf81_ess___Photographically_Curious__Mirrorless
[Overall] Sensor [SLR] Large sensors (APS-C and full-frame) support either larger pixels (more dynamic range, less noise) or more pixels (irrelevant for Web usage, but important if you print very large). Either way, the sensors in SLRs enable very high image quality. [Mirrorless] 
Same image quality as SLR for same sensor size. Systems based around the smaller m4/3 sensors are at a (surprisingly) small disadvantage.
SLR vs. Mirrorless | Photographically Curious
Mirrorless