However.. on the flip side.. MMM are easier to maneuver in tight spots as there isn't a 4' fixed unit hanging on the back of the tractor making for wide clearance turns.. And.. I've found that it is easier to mow 'close' to shrubs and fence lines as the MMM should protrude out the sides of the tractor for best eccicience... and with being mid mount.. you can look right or left and see what clearance you have, without having to turn around and look straight back.. etc.
I don't consider a MMM as a quick change item.. If I have a tractor with a MMM .. it stays on ther permanently.. that tractor effectively becomes a big lawnmower.
Soundguy