Good article on DPS by Andrew S. Gibson about this subject.
(not posting a link here because the knee-jerk reaction from Admin would be to move this post to the links section or to the attic).

Note in my title I say STATIC focusing. Gibson did not differentiate static from dynamic focus in his article so I'm doing it here.

He cites 3 reasons for superiority of Mirrorless over DSLR for static focusing (below is not a copy this is my interpretation of the article):

(1) Direct focusing on the sensor. Lower complexity, no calibration or fine focus adjustments or adjustments for different lenses, are ever needed.

(2) Better manual focus tools. On DSLR's manual focus aids like split prism screens are a thing of the past. The little arrows aren't much help. Mirrorless cameras offer better manual focus tools; Focus peaking or image magnifying functions, viewable through the electronic viewfinder (ELF), which greatly aid in achieving sharp manual focus.

(3) Ability to display additional information like a Hyperfocal distance tool which displays information directly in the ELF.

All of the above rely on the ELF which shows exactly what the sensor is recording. DSLRs do not have an ELF. Some people still violently prefer seeing the scene through glass rather than a picture of a picture. However ELF's over many advantages over optical. Maybe in the future someone will offer a DSLR with a "live view" functions that is visible through the optical eyepiece and switchable from optical to live view.