JK, I've had multiples of all 3, and have taken elk with all 3. At the end of the day, I prefer the 84M over the 84L. The 308 Montana is the Kimber "no-brainer of the century award winner."
My experience is opposite Brad's.
I find the 84L, with its longer LOP fits me better, and therefore points better.
I owned 84M Montanas, needed to shift my head enough when I shouldered the rifle that I sold it, regardless of scope. Wanted to like them, didn't.
The 84L is a point and shoot weapon.
Currently have three, two of which are Montanas in the AI and .30-06.