Agreed. They are different.
I love my 40D and it is very capable, but 1.6X crop can't do narrow DOF like FF can.
I've posted threads here showing how good 1.6X crop is c/w FF and trying to dispell myths about the 5D, but 1.6X crop can't do DOF like this at these aperatures....(I know because I took the same shot with my 40D and the greater DOF yields a very different looking shot).
5D, 85 1.8, f/2
5D/ 85 1.8, f/2.5...
do you have shots with the same scene taken by the 5D and 40D? if so, please post - i'm curious to see them