If you got the room, go with a RFM.
While the MMM is a space saving device and slightly more maneuverable, I've found that the older you get, the harder it is to connect them. Gets old crawling around on the floor.
I've got a BX2200... with the MMM. Would I get it again with a MMM? Absolutely not. I would spend the money on a KingKutter finish mower.
My MMM has been rebuilt several times. Mostly the left and right spindle bearings go south first.
I will be on my second rebuild of my MMM gearbox as it developed a slow leak from the bottom seal. While I'm in there, I will tear it apart, check the gear splines for any abnormal wear or damage. Then replace all bearings. Personally, 2500 RPM for a gearbox is a bit much. Even though it don't got a tach, I run it a tad slower, probably in the neighborhood of 2200 RPM, which between that and yearly gearbox oil changes, it has served me well this time around. Last time I rebuilt it was 7 years ago. Probably has 1,200 hours of mowing since last rebuild.
Once something severely breaks on this MMM and it's no longer cost effective to repair, I will go with a 60" RFM.