23fbaf81_ess___Photographically_Curious__Mirrorless
[Overall] Body size and weight [SLR] Larger (has to contain the mirror box) and heavier (more hardware: two mirrors, AF sensor, viewfinder prism). Pro-level bodies are especially large and heavy. [Mirrorless] 
Nicely small and light. Some (but not all) models are too small, to the point of being uncomfortable to hold. Less advanced models can be made as small as compact cameras but with the advantage of much larger sensors and thus higher image quality.
SLR vs. Mirrorless | Photographically Curious
Mirrorless