GHz and how many I want.

I'm buying my first Mac tomorrow and i'm almost certain i'm getting the 21.5" 2.5 GHz and the 500 GB hard drive, but I started looking at the 2.7 GHz with a 1 TB hard drive for $300.00 more. Disregarding the hard drive size, is the .2 GHz worth the 300 dollars? And if it isn't, is the hard drive worth it?