If everything else seems pretty equal then look beyond the basic specs., though you still can find things there. This is what I found when looking at those choices:
Massey, larger backhoe bucket, 6" more digging depth, and much smoother, more powerful backhoe function at lower rpm, more hydraulic function at lower rpm too.
JD, a bit more ergonomic to me, good options for aftermarket stuff, more loader choices, and standard qc on the loader bucket, larger engine than Kubota, etc. It is also the largest of the 3 you are looking at. Loader, and forks are designed for larger tractors, front blade, and the 47" snowblower then available designed for smaller tractors, and all not quite as well intergrated as the Kubota, and perhaps Massey.
Grass collection is more difficult to install on any of these tractors than on lawn / garden tractors. I haven't seen a Massey collector, but it doesn't look too bad, and is powered by the pto. The JD would be next in ease, and is powered by a belt off the mower deck, the Kubota seems efficient, but looks like a pain to empty, and install, and also has a reputation for eating shear pins.
Confused now?
Kubota BX, most aftermarket options, cheapest in my area, good size, and very well intergrated implements sized for that tractor.