I ride an 06 M-7 and it is indeed an overachierer for a 700. But a guy your size shouldn't be considering an M-7. The M-7 is very good in soft snow and is very easy to toss around, but the power will not be adequate for someone your size, especially the low end power. Not only is the bottom end soft, but the fuel injection mapping sucks as well, and you experience part throttle stumbling in many conditions and some of these are at bad times. Look at how many threads exist regarding flat spots in the power band of people's M-7's. Also, they absolutely suck on the road...both the rear skid and the skis. And don't forget...NO REVERSE!!!
The Rev chassis is much harder to carve with (ridden them many times) and definitely will take some adjusting to. Even so it is easy to sidehill, will climb like a goat, and has an excellent ride on the rode (sled pretty much pivots under you through the bumps). Plus it has an awesome powerband; I love the power and how the front end just pops up when you gas it. The way the nose pops up makes them feel even lighter than they are. Also, even though the earlier 800HO had less HP than the newer Powerteks (07 and later) have, they have a much stonger bottom end (power wise, not strength wise), so I think they are even funner to ride while boondocking. The powerband of the Powertek 800s feels more like a Polaris...softer on the bottom but a strong top end. And don't forget...ELECTRONIC REVERSE!!!
So, it was only between an M-7 or a Rev for you...Rev all the way! Just be sure to look one over very carefully, because the nuns do bend easily and someone could sell you a sled that is already tweeked. When you look one over...tip it over and look at the A-arm angles relative to the centerline of the sled. This is the easiest way to judge if the nun is tweeked.
Now if you are a Polaris guy at heart and you bleed red, then why not wait until you can get yourself a newer IQ 800 (again, NOT A 700).
I would also suggest the 09 M-8 if you could swing it, but you were specifically asking M-7 or Rev (I haven't seen much difference in the earlier M-8s relative to my M-7).