Recursively diffing all of the acctual files on each box probably wouldn't have been a good idea, but i've never had a problem diffing sorted lists -- no matter how much difference there is. (I'm curious as to exactly what you found with google convinced you diff would have been bad)

As many people have allready pointed out, "comm" works just as well (if not better) then diff ... i just tend to dislike the whole "tabed" output of comm ... but "comm -1" followed by "comm -2" would be great if you didn't mind having two seperate lists.