23fbaf81_ess___Photographically_Curious__Mirrorless
[Overall] Additional features [SLR] You can view and compose without turning the camera on. [Mirrorless] 
Bright viewfinder image even when the light is low, image magnification when focusing manually, focus peaking (highlight areas in sharp focus), image review and menu settings are possible in the viewfinder. Light entering through the viewfinder does not fool the exposure meter. On the negative side, you cannot look through the lens and compose when the camera is turned off.
SLR vs. Mirrorless | Photographically Curious
Mirrorless