What are the differences between the 2 in a dually version?

The 450 has heavier axles and springs, bigger brakes, a slightly wider front axle which allows a much tighter turning radius. It also has much higher tow ratings.

Go with the Sportchassis
Rides better, better mileage, longer range.

Dont have a 100k or i would

I started a thread along these same lines and got a few answers but I went to diesel stop and got a lot more. It looks like there are very few differences between the two. I thought the brakes were bigger but with the smaller wheels on the '11 it looks like they are the same. It looks like the biggest difference would be the gear ratio and in turn the mileage.