Mac OS X 10.5.6 delivered a slightly higher MIPS count when running a speed test with 7-Zip. This was a slim but still evident lead over Ubuntu.
At compressing a 2GB file using Gzip, Ubuntu 9.04 required less time. Ubuntu has not yet switched to using the EXT4 file-system by default, but when it does this number should improve more in Ubuntu's favor.
When it came to encrypting a 2GB file using GnuPG, Mac OS X 10.5.6 was faster. At file encryption, Mac OS X with its Journaled HFS+ file-system was faster by about 6%.