I much prefer my dovetailed column mills to the old Emco U3 round one so have used both types.
Although you say the datum can be picked up with a wiggler etc the problem is usually caused when you are drilling and changing to a larger diameter drill means raising the head due to the increased length of the drill bit, this will now mean that the average wriggler or edge finder is too short so harder to relocate datum without lowering the head again and then you just go round in circles.