Actually, I'm forgetting my own software.
For both Android images (boot, recovery) and ELF images (xbl, abl, rpm, cmnlib...) the /t flag only loads the "truncated" image.
So you can:
Code:
edl /u /r /t /pwhatever_a a.img
edl /u /r /t /pwhatever_b b.img
fc /b a.img b.img | more
This will generate files only as big as the "real" content.
So when you compare the files you won't be comparing the dust bunnies at the end of the partitions.