Having a LOT of seat time on a rev and more then enough time on an M sled t ojustify both... your 1 single comment made it clear to me... you like to spend time on the trails, the rev hands down crushes the M in that categorey, they are much more stable. M will out sidehill the rev, but i have found that as someone who has learned the rev chassis, its not about the sled, its the rider, the M is easier to learn, but given time the rev will not be left behind in any way.
Honestly, for what your doing, they both seem like great sleds thought.. where do you live, and which is the better dealer in your area, probably the biggest thing for me. although man, i LOVE to ride M sleds, i dont know if i could descide, i love M's and man i love my DOO's. get a yama-doo... there the coolest.