5D or 5D MkII?

[Jerry Gowins]

This is a question for those of you who have used or owned BOTH of these cameras.

I own a 40D and love it.  That said, I borrowed a 5D for my trip to Santa Fe last year and the 40D never left my bag!  I love the IQ from the 5D.  The lenses I used were the 17-40mm L and 24-105mm L.

Is the IQ and higher ISO capabilities of the 5D MkII that much better than the 5D?

Thanks!

Jerry