As long as you are set up to use one or the other there is no difference. To spot correctly your spotter needs a reticle with the unit of measure you are shooting that way he can give you an instant call on the splash or dirt so you can get another round in the air if needed under the same conditions.
The only thing that speeds the call up is measuring it in a reticle you are spotting with.
With that said, at tactical matches you see more Mil. set ups.
