I agree that you need to determine what your riding needs are. I actually like the touring sled 1 up...it is very smooth and stable and has more of a soft ride. I also have a Ski-Doo MXV Rev-800 and that is like a sport bike on snow. You have to stay on top of it all the time or it will get you into trouble.
The other thing to think about is whether you want to stud the sled. I have both of mine studded so I can go out on the ice. On the lake, studs let you stop and provide traction; however, the trail performance is a bit different. Some people like to have the rear slide a bit more. Here are some of the sites for your reading entertainment:
http://www.arcticcat.com/snowmobiles...sp?y=106&c=109
http://www.ski-doo.com/en-US/Snowmobiles/2006/
http://www.yamaha-motor.com/sport/pr...06/0/home.aspx
http://www.polarisindustries.com/en-...s/Performance/
Here is a buyer's guide:
http://www.amsnow.com/sno/default.aspx?c=bg&id=21
When you get to the point that you are finalizing your selection, try to find someone that owns one. Ideally, try to ride it first.
jetskier