If #4 uses the Turion ML-34 you probably don't want it. That's the older 35W version. It runs hotter and reduces battery life vs. the 25W MT-34.
None of the processors will be as fast as the Centrino Duo. I'd guess speed rankings at:
Code:
CPU Video
System 1 1st 1st
System 2 2nd 4th
System 3 3rd 2nd
System 4 3rd 3rd
(cpu's will be close besides the dual-core)
Avoid system 2 if you really care about games. The video performance will be poor. I also haven't been impressed with chipset performance of recent Toshibas. Games will care more about the video and chipset differences than the relatively small differences among those CPUs.
I'd start by comparing screen appearance, then depending on the apps you'll run choose among the top three. For me it would be system 1 or 3 bumped to 1GB RAM. I usually prefer AMDs but not for this set.