I have a BX 2350 with a 60" mmm. It cuts very well but is a pain to take on and off. I use the FEL with it on but have to be careful about running over dirt piles and it limits how close to things you can get. My major FEL work is done so it's not so much an issue for me. If you use the tractor for a lot of FEL stuff, I'd go with a RFM because you can drop it easier. I would consider a 60" though for more coverage . The tractor would have no problem with it.
If I could go back in time, I'd buy a tractor for tractor work and a ZTR for mowing. Tractors can mow very well and in rough areas can't be beat, but a ZTR will cut your time in half , if not more, do a better job, and be ready all the time without swapping implements. I find that I leave the small FEL jobs till fall when I drop the MMM for the back blade and get ready for snow. The MMM is just a pain to fit in places and is easy to hang up in rough ground. Maybe it's me getting older, but I like more and more to make my life easier.