Stupid question #962641: which Interchange?

Hello everyone:

I am ready to install Interchange in my server for the first time.
My goal is to provide e-commerce to any virtual domain requesting the
service.
Hardware capabilities are not a concern.

My question is:
Which Interchange version should I install?
Interchange 4.8.7 or interchange 4.9.7?
Why?

Should I install from the tarball or the rpms, given that I will be
hosting several virtual domains?
Red Hat recommends tarball for multiple virtual domains for Interchange
4.8.X, but what about interchange 4.9.7.

I am running in a tide deadline and I am ready to fire up that
installation (after *WEEKS* of research!), so I will *REALLY* appreciate a
prompt response (like the day before yesterday...    :)

Thanks!!!
Enrique A. Troconis
Kitepilot Solutions LLC