Hi Bear welcome to the forum. I don't remember anyone writing in with a problem with an M6. This could be good news or simply because there aren't many out there yet. You can't search this forum with just M6, not enough letters, and M6-101 yields nothing. So wait around for a while maybe one of the guys will log in that has an M.
ROPS or cab?
I have an M9960 ROPS (drive beneath trees quite a bit). It has been flawless but it only has about 55 hours on it.
I would suggest cast rear wheel centers for weight. I have cast centers and weights on my 9960. I never use liquid ballast as I change all of my own tires.
Not familiar with transmission options on the 101 but I would suggest the 6X2 if the 4X2 is standard equipment. Of course the power shifting 6X2, 24 speed is even better if available.
Other options depend mostly upon what you plan to do with it.
Sorry, this should have been posted in response to the OP.
SDT