Which is less intensive on computers?

Hi I'm unfortunately using a really crappy old computer while i wait for my new G5 to arrive (i ordered it a week ago today) so i was just wondering if running protools 5.1 would be easier on the computer than 6.4? It might not make any difference but I'm not sure and thats why im asking. Thanks

oops, 5.3 not 5.1.

My new computer (which is yet to arrive and won't even run protools yet anyway) is a dual 2.7Ghz powermac but in the meantime im running a pc with a 2.8Ghz pentium 4 processor but stuff all ram (256mb shared with graphics ) and it doesnt seem to be working too well at all. Maybe i should have posted in the pc section but i just assumed if either version of protools was more efficient than the other it would be the case for macs as well as pc's.