Replying to Getting a macbook pro, I have one quick question NS

Ok guys I have a quick question here about the macbook i'm gonna be getting for this fall at university.

I can get either the 2.4 GHz macbook pro with 4 gigs of RAM and the 3 years of AppleCare for the same price as the 2.5 GHz one with 2 gigs of RAM and no AppleCare.

What should I get? I don't get it, why is 2.5 GHz so much more money than 2.4GHz, is it really that much better? As far as I can tell thats the only difference. I mean the 2.4 GHz is the same price and it has more RAM and the AppleCare. I'm no computer expert though.

Also, what is better, a 250 GB hard drive @ 5400 RPM or 200GB at 7200 RPM?