Ok, bear with me cause i really don't know anything about computers. I decided to get a Dell for college and it's a studio 15. I'm either getting a "500GB SATA Hard Drive (7200RPM)" or a "640GB 5400 RPM SATA Hard Drive". Thing is that I thought the more RPM, the better the computer performs, or is it just storage? So whats better to get, less GB but higher RPM, or more GB but less RPM. Perhaps im totally misunderstanding this so please, and info is appreciated.