Raid 0 performance: 2x WD Black Caviar vs 4x Spinrite?

As title states, I'm wondering if it makes any sort of sense to go with

4 x (or 3x if the jump from 3 to 4 is negligable) Samsung Spinrite F3s

Over a couple of 640gb WD caviar Blacks?

The spinrites would be $50 more for four.

Can anyone give me any sort of numbers as to what I'd experience with either config?

This is for a video machine, I pursue a regular backup cycle and data loss \ failure isn't really a worry.

Thanks