Here's the impressions I have between the two chassis.
M-series pros:
Holds very steep side hills a little better. Narrower a-arms may actually negatively affect this.
Very predictable handling in all aspects: up, down, and sideways.
Very wide balance point.
Easy to work on under the hood.
M-series cons:
Suspension leaves a lot to be desired on anything rough. A Pro RMK still feels like this too.
Feels a little more planted and not as easy to initiate a roll up onto its edge. Narrower a-arms will help you out here.
Proclimb pros:
Easier to initiate the roll to its edge.
Responds to rider input quicker.
Suspension is much better in every aspect.
Handles cutting across rough, rutted, trenched out hillsides well without bucking the rider.
Much more predictable to jump (if you are into that sort of thing).
Proclimb cons:
Not quite as easy to hold extreme side hills without narrowing the boards and sucking in the side panels.
Some of the bodywork seems cheap and will require a little silicone to seal up some gaps up front.
Working on anything under the hood takes more time.
My favorite thing to do is ride steeper treed hillsides and I won't go back to an M-series. A 2014+ proclimb is just a way better all around sled. You do have to ride more forward on the Proclimb and ride with your feet up towards the footwells as your natural position. Once you do that it becomes easy to ride. If you try to ride it like an M or Pro RMK with your feet set a foot back all the time you will fight it.
As a side note, my Pro-Lite sled was weighed on a set of scales and came in at 540lbs wet with a spare belt, tools, and muff pot. My buddy's lightened M7 was 548 in the same trim. I have the 38" front end set on the wide setting and his was stock 40" set narrow. Sitting next to each other in the parking lot, mine was significantly easier to roll side to side and tip up. So there is more to be said about weight distribution and centralization on a sled than just it's weight number.
