whats the difference?
The answer is 0.04 
Actually I don't know what has been changed in the file system itself between these two versions. Usually the major changes are done in the VMFS driver rather than in the file system. (see an older post at http://www.yellow-bricks.com/2011/02/25/re-vmfs-3-versions-%E2%80%93-maybe-you-should-upgrade-your-vmfs/)
Anyway, I moved the discussion from 4. Storage VMFS to VMware vSphere™ Storage in case someone knows.
André