Vista, or XP?

Hi all!

I am about to install a new system. I have Win XP Pro laying around
here, but also RC2 of Windows Vista. Which should I install?

The end-user of the system prefers Windows Vista, but also the least
amount of possible hassle...

Since he'll be wanting Windows Vista Home Premium when it becomes
available, I am wondering what path to follow:

I XP now, upgrade to Vista Home Premium later
II RC2 now, side-grade to Vista Home Premium (is this possible?)
III XP or RC2 now. Fresh install of Vista Home Premium later


The 3rd option is obviously the one with the most hassle, but also the
one that will give the cleanest system...

Is option II possible anyway? Or can the RC2 (which is Vista Ultimate),
only be turned into Vista Ultimate?



Regards,
Evert