[quote name='Jimmypaine']OK - here's a question...if you bought HR today, I understand that you can download the PS Move patch - but it's about 2GB. But if you imported the "Move" edition from outside the U.S. - I think it's safe to assume that patch is already on the disk...but does the game require the same "patch" data to be installed to the HDD?[/QUOTE]
Both of them require an installation, and they are quite large. Regular HR needs 4.5GB (plus 2GB if you accept the patch) and Move Edition HR requires about 6.5GB (two installations, both required for play).
The other pros to importing besides the Move stuff would be the DLC, dynamic themes, soundtrack and making-of videos that also come on the disc.
I would consider upgrading your PS3's hard drive, if you can. It's only going to become more and more of a problem, Heavy Rain or not.