Depends on what you want to do with the sled really... and this is just my opinion... I don't want to start any arguements lol... (remember opinions are like a$$holes... everybody's got one lol ) a mountain max is a long deep lug track, geared low for deep snow and hill climbs, not really designed for top speed lake running, more for pulling up the skii's and playing in the deep stuff..but still a force to be recon with on the trail and a super comfy ride due to the long track...but if your looking to go with a fast and lake run/race then the SX-R Blue head would be the choice i would think... Again.... just my opinion. The red heads are a great strong motor and can be tweaked nicely... only issues i've head about is watch out for the waterpump.. the gear that runs the waterpump and oil pump off the crankshaft is pressed on to the crank and has been known to slip.. requiring the crank to be removed and the gear pinned to it.. 3 cases of it that I know of here in sudbury and im not sure if the blue's share the same crank or not.. i believe after 2001 they came pinned from the factory maybe somebody can confirm this for me?) The blue heads have the power valves and typically make more HP out of the box. I think reds were in the 115-120 HP range and the blue's 130ish. If you find a MMax and your not intrested let me know i might be..
Thats my 2 cents worth.. take it or leave it lol,
Have a good one, keep'er rubber side down!