This is a repeat answer for me, but sometimes repeat answers are a good thing, if they are still useful.
I have a
B2910 with 72" MMM and a
B2150 with a 72" rear discharge finish mower. In general, I like mowing with the mid-mower better than the rear mower. But they each have their advantages.
MMM Advantages: I mow on some pretty steep slopes and I feel that the MMM adds to the stability of the tractor (most of the weight being below the center of gravity) while the rear-mower takes away from the stability of the tractor (it is still below the center of gravity, but has a tendency to want to pull the tractor sideways when mowing across slopes).
Rear Mower Advantages: The rear mower is much better when it comes to maintenance, and for mowing some areas (such as over a bank) where you don't want the tractor's wheels to go. I have some areas where the rear-mower is the only mower to accomplish the job.
Here are questions to ponder for persons with the mid verses rear mount dilema:
(1) What percentage of time is the tractor spent mowing compared to other tasks, and can the other tasks be effectively accomplished with a MMM installed? If you have to frequently remove the mower for other tasks, then the rear mower may be the best choice.
(2) Is the terrain level or sloped? In my opinion, sloped terrain favors the MMM because of tractor stability issues.
(3) What are the mowing obstacles and challenges? Mowing around trees favors the mid-mower, but mowing under tree limbs favors the rear mower because you can back the mower under the tree limbs.
(4) Will others be using the tractor? I think the rear-mower is more challenging to use for my wife and children, but not a problem for me.
Hope this helps,
Kelvin