I had a 2004 600SDI and bought a 2005 500SS. For the difference in price, the 500SS is the better way to go. My 600SDI blew up at 5500 miles. The 500SS has 10,000 miles on it and I will run it this coming season. The 600 SDI got 17-19 MPG and 140 miles to a qt of oil. The 500SS gets 15-17 MPG and 150 miles per qt of oil. The 500SS will stay with most sleds. My bud has one and he will run with SD 800's and AC F-7's. A lot of that is the rider but fact remains he stays with them. This was on trails, not on a lake. I can't justify spending $1,000+ more for a 600SDI over the 500SS. But to each his own. Spend your $$$ the way you want too. You earned it.