I realize you've made the decision, but I thought I'd offer my two cents:
People keep talking about reliability comparisions. We had two m-series sleds, and I never once fouled a plug. I always changed them at the beginning of the season just for good measure, but never needed to in midseason. Sure, the suspension bushings wore quickly, but that is cheap to repair, and preventative maintence.
I actually prefer the 4-stroke world to 2-strokes, but we have two dragons, mostly because of the weight.
Also of consideration on a topic like this, is what is the sled that most of your members ride on their own time. It would be nice to have sleds that were as close to that as reasonably possible, so when on a search/rescue, your riders are not learning quirks that a different chassis has.
I think you made the right call for your intended use, by selecting the M-series for your purchase.
PE