It's totally up to you.. The difference will not be huge, but you will notice generally "snappier" response from your system, and probably faster boot/loading times if you go with the Raptor.
However the 500GB is no performance slouch either and I think you would be comfortable using that as a daily driver.
I personally have 2 150GB raptors in RAID 0 for my OS drive, and 2 500GB's in RAID-0 for my storage drive... and honestly, apart from HDTach telling me the raptors are faster, its tough to tell when using disk heavy apps like video editing.
My honest advice would be to save the $115 and invest it in a better Graphics card or CPU.