About to order the MBP but I wanted to know: Do I get the 120 Gbyte 5400 RPM drive or the 100 Gbyte 7200 RPM drive? I know I will use the space, but if the speed of the hard drive takes a hit on the overall perceived speed of the computer than I want to know. I am going to film school but I edit off of external drives (Mac HD is STRICTLY FORBIDDEN!) Soo... What do I get? Will I really notice the drop in speed? Will I regret not having that extra 20 Gbytes? Help?