Did a quick comparison of some Linux compression options. I created a tar file (no compression) of my entire /usr/share/doc directory. It's just about 189 megabytes for the whole thing.

doc.tar = 197314560 bytes
doc.tar.gz = 68900135 bytes
doc.tar.bz2 = 59759701 bytes
doc.tar.rz = 56659057 bytes
doc.tar.7z = 55134551 bytes