Eliptical or Treadmill?

Looking for some input.

What do you guys think is a better machine for home use for cardio? I know the eliptical machine is supposed to be better for your knees. But does one burn more calories than the other?

Does anyone have any recommendations? Models, etc?

ttt

I got my elliptical for like $600shipped from Sams club online. I bought it for the exact reason that you described. Low impact on the joints.

Very good article here:

http://www.mercola.com/2002/apr/24/treadmills.htm

Awesome...thanks!