I had an Polaris IQr for a time. It was stretched to a 159 so a little different, but from others who I talked to (I rode with 2 guys with 600RS Doos last week) you will LOVE the race chassis for off trail set-up or medium depth conditions (track length does make a difference).
As for trail riding, I don't think they tend to hold up as well. The real stiff lugs on the race tracks tend to break on hardpack, and the motors are pretty high strung. they like shorter WOT bursts rather than the duct tape and ride theory.
They also do not have sway bars so they will handle more like a mountain sled than a trail sled on the trails.
I would love to have a shorty race sled as a second sled, especially for spring riding!
Blutooth