One thing that is missing from the Core-i5 is VT-d support, which apparently is some kind of I/O emulation acceleration (I assume it stands for VirTual-Disk). Does VirtualBox support this now/soon?
The i5 seems to support Nested Paging - can anyone confirm NPT as Intel is a bit wooly - their website is as bad as Sun/Oracle's
The i5 has VT-x support for certain, so if VB doesn't support VT-d and the i5 does in fact support NPT, its a bit of a waste of money going for the i7 (who wants HyperThreading?!)