Interestingly, I have 2. A venerable M9 (The tractor that I always considered to be the 4020 of Kubota, the longest running production large frame tractor that Kubota sold)
My M9 has the optional creep transmission and the dual speed 540-1000 pto. ....has the hydraulic shuttle and a hydraulic main clutch. I typically run all the hay tools with the exception of the BR780 round bailer with it and it handles everything just fine. I bought the M after Kubota discontinued that series, ordered it and waited 4 months for the tractor (my dealer had to make sure that Kubota still had the necessary components to assemble one and they did). It is a 12x12 transmission, 4 on the main box and 3 on the auxilliary.
I also have a 105S which is the new style cab and ac with low vents and oval cab lights. It is a 12x12 power shift. The 105 and the 9 have the same 4 cylinder turbo charged air to air engine and both operate at 540 at the same engine rpm, 2250. The 105 is only 540. It stays coupled to the BR780 because the computer that controls the bailer takes some cab room and it's easier to just use it for round bailing. The 105 came in an X version with joystick on the armrest electric powershift. I didn't get that.
The M is 83 PTO and the 105 is 90 PTO, both have plenty of grunt, good on fuel and comfortable. Both have cast rear discs and both have double sets of remotes and draft control (not that I use it). Both are excellent utility/forage tractors. I was more concerned with torque rise than actual horsepower. It's the torque rise that gives you the power to run implements, especially round bailers, where, as the bale size and density increases, the engine has to be able to hold a steady rpm as the load imposed increases, that's where torque rise comes in.
Both have quick detach front end loaders but the 105 has the long parallelogram linkage. The M has the short, conventional linkage. The capacity is more than enough on both loaders for anything I do. Both dismount fairly easily and remount so long as you keep in mind the physical size of the loader. Neither is a little tractor, consequently, the loaders are large.
I did opt out of the Kubota QD attachment on both tractors and replaced the QD front's with ATI quick detach Bobcat style plates that have industry standard spacing so I can quickly (in about 5 seconds), change out implements.
Both are very fuel efficient and I'm happy with both though I do run the M a lot more. It's my favorite.
The 105 will handle an 11 foot disc mower and/or discbine no problem or just about any Cat 2-3 rear mount implement.
I'd recommend a use, low hours M9 as well (if you can find one). Mine isn't for sale.