I have both, they are both great scopes and wouldn’t hesitate buying either. Great glass on both but for my eyes I think the MK5 is notably better. Brightness on the MK5 is also better. Tracking quality identical on both. If I had to only chose one based on glass alone, MK5. Some of the things I don’t like about each:
MK5: limited to 3 revolutions on the turret. I have 60MOA built into the base and the mount and have a full three rotations of the turret but wish I could use the remaining elevation.
Toric: locking turrets are nice, but to lock the elevation after making an adjustment the turret has to be “massaged” to drop back down into the locked position. Nothing Wrong with the locking mechanism but it is noticeable and wish it was smoother.