I ride a 05 Renegade 600SDI and I have a friend that has a 06 Crossfire 700, here is my take on this:
The Renegade is a better trail sled as stated above, it simply is a better ride over the bumps and such, it does sit a little higher like a dirt bike.
The Crossfire sits a little lower and does corner better because of a lower center of gravity, it is a blast on a Sunday morning after the trails were groomed. The seating position is very much like a quad. I also like it better off trail due to it being easier to carve and side hill. Seems to protect the rider a little better from snow over the hood (for all the times that we get that much here in lower Mi!!!)
The Crossfire has a better guage set up and better wind protection, but it is prone to running hot due to the small cooler as mentioned above also m(early build 2006). I would definetly buy a set of scratchers. I have never had a problem with the Renegade running hot.
The Renegade gets waaaay better mpg and goes thru almost half the injection oil, but I would take that as a trade off for the power of the 700 anyday as it is a blast to ride.
Both have very good and dependable motors and are good choices. From what I have seen pricewise the Crossfires can be found cheaper based on year/mileage than the Renegades.
It could come down to which brand your local dealer services.
I love my Renegade, prefer it over the Crossfire due to the seating position, but would love to figure out how to put that Cat 700 motor in it!
I will be in the market next year to add another sled to the fleet, wanted to do it this year but could not swing it. I will shop for eithere a Crossfire or Renegade and will buy the best deal I can find. But if it comes down to apples to apples I will buy the Renegade again!