Pc 3200 or pc4000?

So in a system with an abit nf7-s, barton 2500+ which would lead to better performance and stability? and why?

Corsair TWINX512-3200C2 2x256MB PC3200

or

Corsair TWINX512-4000 2X256MB PC-4000 DDR500

I ask mainly as i dont see a large price difference, but the timings are slightly different.

Is there one better than the other if its overclocked? what if its not? (but it will be, just trying to learn)

Thanks for the info guys.