Compare two oracle .dmp files
Comparing dmp files like that is probably quite difficult to do, as the format is quite complex, with snippets of embedded SQL and all sorts.  Having said that, although it is a binary format, it is a stream format (i.e. no internal pointers), so it's quite amenable to processing with sed.

I think loading the contents of he dmp files into two schemas and comparing the two is by far the easiest way you're going to do this, barring the existence of some tool that I'm not aware of.