I'm getting a MBP 15" and I've picked out all the specs and am about to pull the trigger. I'm just stuck on this hard drive thing. Not sure If I should go with the faster 500gb drive or the slower 750gb drive. I have no idea how big of a difference the two are in terms of speed? I'm pretty sure that 500gb will be enough space for me but it's always nice to have a bit of extra space.