Hard drive cache

I'm thinking of getting a new hard drive, and i'm wondering what performance difference is there between a harddrive with 8MB cache or 16MB.

I remember when the 8MB ones came out, several sites did reviews and said performance was nearly the same as the 2MB ones.  If you want performance, get a 15krpm drive for those files and a slower one for things where speed doesn't matter (stored video and music since playback needs hardly anything, etc.).