I'm looking at buying a new MBP, and I was wondering how noticeable the difference in performance is between the varying HD speeds. I'm either going to get the 7200 160gb or the 4200 250gb. They make 200+gb hd's with faster than 4200 speeds, surprised apple doesn't have them. Anywho, just wondering where I'll see performance drops and where if I opt for the 250. Thanks.