Go for the 500ss. If I were to buy a rev that would be my choice. The 500ss (really a 600) is rated at about 110 hp and is a very reliable engine ( probably the most reliable ski-doo has made) The 550 I'm guessing is around 70 hp?? You'll be happy on the 500ss 3 years from now, I don't think you'll be happy with the 550 after one season.

 

The 500SS is a liquid cooled engine that is almost a 600 with a 1" track. It should be a bit faster. The 550X has a better suspension (HPG) and a 1.25" rip saw track. You also get internal/external drivers, racing seat, acerbis handguards, riser block, braided brake line, tunnel reinforcment and the new tail light configuration (supposed to be about 2 lbs lighter). The 550X is rated 35LBS lighter overall than the trail. Can you guess which one I might suggest if you arent out to race everybody across the lake/field. The 550 fan will have probably about 65HP and the trail should be around a 100HP, I think. Ive sat on the X and its a really nice machine. I have not seen the trail up close yet. There are advantages to the power of a liquid cooled engine, but the 550X has alot of nice riding upgrades.

 

the 550 is a fan cooled motor. the 500ss (series3 600) is a liquid cooled motor. you will be much more happy with the 500ss and more power.

 

Get the 500ss alot faster than the 550 fan.

 

Last year I also looked at the 550's and the 500ss, I went with the 500ss mainly because for a few extra $$$ I was able to move up to a 600cc motor with liquid cooling. This was my first "new" sled, I'm not disappointed and I would definately buy another in the future.

 

I'd say get the 550X... 65 hp is plenty of power, i've had a blast on sleds with 25 hp. The better suspension etc will be great. There seems to be some power craze among us sledders, in the mid 80's 65 hp would have been pretty much top of the line for a sled. 65 hp is still 65 hp and as a first sled that's plenty. The 500ss is a great motor i agree. It would be enough for me, i ride a 110 hp big block 600 and that's plenty of power. You heard me, i'm happy with 110 hp and i've ridden sleds since i was little

 

get the ss then if ay sack out the shocks from riding it hard buy older x piggy back ones which look real kool! and i really donmt think they would put internal/external drivers on a fan there really no power there too ratchet the track, i can run my 600 reall lose befor i ratchet my track!

 

I can say with 100% certainty that there are internal/external drivers on the X. I just looked at the one sitting here on the showroom floor. As indicated im my first post the X has alot of nice features but clearly if you want more speed/power go with the liquid.

 

As for speed btw, the 550 about 70-80? Correct me if i'm wrong. The 500ss should be good for at least 90 true MPH on GPS.
Edit: You say you'll be trail riding most of the time, that's another strong point with the 550X. It's lighter and should be really easy to control.