If you are serious about the performance of your MySQL database, I strongly suggest to do your own benchmarks in a test environment. Filesystem performance can vary significantly from one kernel version to the other, and choice may depend considerably on your exact workload.
For a simple comparison, just set up a test server with the same kernel version as your production system, and use sysbench to benchmark xfs, ext3 and ext4.
To have a better view, you would restore a recent backup of your database on your test server and create some scripts that generate load similar to your workload.
Also, every time you plan to upgrade the kernel on your production machine, you should rerun the benchmarks, to see if there are regressions. Since you can't easily switch file systems at that point (well, that depends on your setup), you should at least make sure that performance is not degraded after the upgrade.
BTW, you can find a lot of good advice on the MySQL Performance Blog.