Vista - XML Dif?

Hi,
I am a new user to PowerShell. I have written a small program which will
send a request in XML and get the response in XML, Now I have to compare the
response which I got with Reference response XML. I don't want to comapre
line by line but it should be smart enough to give the output saying so & so
tag/attribute is missing/added in the actual response xml. Is anybody aware
of any such utility?

Thanks,
Nikhil