Prior to this past July, I had a BX 2200 with a 60 inch suspended deck, since then, the B2650 with a 72 inch ground contact deck. While neither can maneuver like a zero turn, I do prefer the 72 inch ground contact mmm.
Normally I cut at 3-3 1/2 inches, so the gauge wheels' height adjustment pins seldom need changing unless you're doing loader work and other 3 pt. tasks. Then pin up the deck (2 pins) and the 4 gauge wheels. Those tasks become part of the routine change over to another implement and take 5-10 minutes.
Aside from that, the ground contact gauge wheels provide extra, excellent flotation and swivel with turns, making them less likely to gouge ruts. The fixed gauge wheels of the suspended mmm are to prevent scalping but my experience was that they gouged turf creating ruts on soft or wet turf especially when turning corners.
The 72 inch extends out far enough on each side of the tractor's wheels which allows one to mow closer to trees etc. without scraping off lights, mirrors etc.
Also, that extra foot per swath over the 60 inch suspended deck adds up on a large lawn, significantly decreasing mowing time.
Add Gator blades and if you can fashion an outlet cover, mulching capabilities are possible.
Add the Cab version of the B2650 and you'll mow in a dust free, quieter, air-conditioned and UVB sun protected environment (some UVA still gets through so you still need to apply broad spectrum spf 50 or higher sunscreen sunscreen).
The drive over feature of the 72 inch deck makes install easier but the swiveling gauge wheels also allow an easier push in from the side and for fore/aft adjustment. The fixed gauge wheels of the suspended mmm require far more effort to push them even if you rotate them the 90 degrees allowed for mounting.