Dr Dan,
I have an older B7100D with a mid-mower (very difficult to remove for maintenance) and a
B2150 with 3 point mower and FEL.
For some parts of my land I prefer to use the tractor w/mid-mower and for other parts I perfer to use the tractor w/rear mower.
Basically, for my property, if I had to have just one, I would have the 3 point mower (as long as I had hydrostatic transmission). I have some steep areas that I go up and down the hill mowing; I would be nervous doing that using the 3-point mower without the FEL for counter-balance. This setup also allows more clearance over humps that I have to cross. When I mow the same areas with the mid-mower, I feel more stable but the mower hits dirt more often on the uneven terrain.
For me, here are the strong points of the mid-mower and 3-point mowers:
Mid-mower stong points: More maneuverable, the 3-point hitch is readily available for most any other task, less space used on the trailer when transporting, less space used when storing the tractor in the garage. Counter-balance is not a concern when on steep grades.
3-point mower strong points: Cheaper, Easier to install and remove, easier (safer) to mow next to the river and next to the edge of steep drop-offs, easier to mow under tree branches. Compatable with other tractors.
Hope this helps,
Kelvin