I shoot sports in dark rooms, and the viewfinder automatically adjusts to the ISO scale, so if it shows detection in the -2 or -3 range, the viewfinder is dark and the focus doesn't work as expected. This is not the case with a mirrorless viewfinder, which would prevent you from taking any shots if you set the ISO level to those values.
Revamped Sony Alpha a6000 Mirrorless Digital Camera: 24.3MP SLR Camera with 3.0-Inch LCD and Power Zoom Lens
103 Review
Discontinued Canon EOS 7D Digital SLR π· Camera Body Only with 18 MP CMOS Sensor
88 Review
Canon EOS 60D: 18MP CMOS Digital SLR Camera Body - Your Next Photography Companion
125 Review
Canon PowerShot A480 camera, black
108 Review