Hi,
usually when I start a pilot project, not critical as it is in your case, I always go for the last stable version.
Mainly because I'm quite sure it has been tested, it constitutes a stable brick of my environment and I have an installer or at least a set of well identified modules.
I would go for a nightly build only if I'm sure it addresses a bug or a flaw that is vital for my project.
But that's always a matter of opinion…
Regards,
Andrea