PiFast
A good indicator of CPU/Motherboard performance is version 4.2, by Xavier Gourdon. We used a computation of 10000000 digits of Pi, Chudnovsky method, 1024 K FFT, and no disk memory. Note that lower scores are better, and times are in seconds. All memory timings are at 2-3-3-5 at 200FSB.
Pentium 4 @ 12x200

Not much of a difference between the TWINX kits, but if we want to nitpick, then yup, the original kit is a little quicker. There's only an average of 0.08 seconds, with the largest gap during our benchmark trials being 0.11 seconds. The ProSeries was never able to surpass the original TWINX though.
Pentium 4 @ 12x250 (TWINX4000 PS @ 2.5-4-3-6)

Score one for the ProSeries as the improved timings nets it a victory this time around.
Pentium 4 @ Maximum OC (TWINX4000 PS @ 285FSB)

Given its ability to overclock better than the others, it was no surprise to see the ProSeries take this one.
TMPGEnc MPEG Encoding
Video editing is a taxing chore, and we'll be testing the TWINX ProSeries using TMPGEnc 2.512 to encode a 7.78MB, 1:30 movie trailer to a 24FPS MPG file. Note that lower scores are better. All memory timings are at 2-3-3-5 at 200FSB.
Pentium 4 @ 12x200

Pentium 4 @ 12x250 (TWINX4000 PS @ 2.5-4-3-6)

I promise to change the movie file in the near future. I guess the short clip isn't enough to illustrate the differences between the ram modules.
Pentium 4 @ Maximum OC (TWINX4000 PS @ 285FSB)

A small one second lead by the ProSeries here. Though a second isn't a lot, as the movie file increases, it's safe to expect the time difference to scale accordingly.