ext2 v1.32 vs. v1.39

[Michael ODonnell]

I note that RHEL3 kernels seem to be unhappy (griping about
max inode count or some such) when asked to mount a v1.39
filesystem created using RHEL5 but the RHEL5 kernels mount
the older filesystems without complaint.  We're in the process
of moving some users forward from RHEL3 to RHEL5 so I wonder
if it matters whether we rebuild their v1.32 filesystems from
scratch (metadata and all) or instead leave them intact and just
replace the files therein.  I've not found anyplace online that
offers straightforward comparisons of the various versions of
the ext2 filesystem, and I'm wondering if there are important
differences, either WRT performance, security or reliability...