git compiled on same distro, different versions

If I only test a new git version (compiled from git.git source) on RHEL6 
before I put it on the RHEL5 box is that sufficient for validation?  Should 
git behave the same on both?  If not, why?

We don't have any RHEL5 VM images so it would be much easier for me to test 
on a RHEL6 VM.  I would have to justify the building of a RHEL5 image just 
for this purpose.

v/r,
neal