Ubuntu 10.04 was faster than Mac OS X 10.6.2 with MAFFT, a computational biology benchmark.
Mac OS X was many times faster than Ubuntu 10.04 when it came to the PostgreSQL performance. This is most likely due to Mac OS X running with the Journaled HFS+ while Ubuntu 10.04 is using EXT4, which has been struggling with this database test in recent kernel releases due to changes affecting the overall disk performance.
Ubuntu 10.04 LTS was much faster with Sudokut, a Sudoku puzzle solving benchmark.
Ubuntu 10.04 LTS was also faster with the Crafty chess benchmark.