I have been shopping around for a 100GB - 120GB hard drive for my macbook. Right now I have the stock 60GB. I was curious if anyone knew the difference between the Seagate Barracuda, and the Seagate Momentus. I know one is 7200RPM vs. 5400RPM, but the one that is faster costs less, so I am kind of confused. Is this because it will slow the rest of my system down? Will 7200RPM even work in my macbook?