Yesterday Phoronix published an article benchmarking the ext3, ext4, xfs, btrfs and NILFS2 filesystems based upon the 21/06/2009 daily build of Ubuntu 9.10 (Linux 2.6.30). The tests used a 7200RPM SATA 2.0 Seagate ST3250310AS drive and unfortunately didn't use any fast Solid State Drives.
Kudos to Phoronix for producing a wide set of benchmarks. The results show ext4 proves to be a good all-rounder choice. However, a few things to remember are:
1) Ubuntu 9.10 will be 2.6.31 based, so expect some improvements with btrfs in the newer kernel.
2) Ubuntu will have some SSD based optimisations, such a aligning the partitions to natural flash block boundaries to squeeze more performance out of SSDs.
SSDs are becoming more popular on netbooks and laptops, and with the benefit of excellent random seek time and fast parallel block read/writes (assume 2,4 or 8 way native striping on the SSD) the landscape may change with respect to benchmarkable filesystem performance.
I suspect we will see btrfs get tweaked and tuned more over the next 6-12 months, and perhaps ext4 will lose it's crown on the Phoronix tests.
What ever happens, the move to SSD and the focus on ext4 vs btrfs will lead to faster booting and more efficient filesystem performance. Onward and upward!