I would compare prices and see what the difference is between some kind of dedicated mower and the MMM.
The MMM is not that big of a deal to put on or take off in my opinion, but if you had a dedicated mower you would have the grass on 3/4 acre cut in the time it took to put the mower deck on your
B7500 and take it back off again...
You also would probably want to take the loader off when cutting the lawn, if it is a lawn you are shooting for rather than a yard.
But using the tractor has to be more enjoyable than using a walk behind or cheap rider mower...
Still...if 3/4 acre is all you plan to cut now and forever, a dedicated machine may be the way to go. Now if you are going to continue to expand the lawn over the coming years, the advantage could go to the tractor mounted mower.
A RFM could be the way to go. It is cheaper, can do a pretty good job of mowing, and is just another implement to hook up to the back...depends on how many things you have to cut close to and around though. A RFM did not really suit my needs...but it did cut well.