2-3-2-5 (OCZ Platinum) would be faster than 2.5-4-4-8 (Corsair Value Select)
(the lower the timings, the better)
Of course, I wanted to save money, so I got the Corsair Value Select.
But, in real world benchmarks (gaming), you could see up to 10% improvements in frame rates (going from CAS 3 RAM to CAS 2 RAM). It does count but it depends what price you can get for them. I expect the 2x1GB kits with good timings to go down in price in the next couple of months.