The reason that the Optimus S performs better in practice is that it actually has a dual core processor 600 MHz application / 400 MHz modem processor. Look at LG's site. Click on the specifications tab.
The Optimus also has a much better GPU (I've heard it's the same GPU as the N1), which makes a huge difference in games and overall responsiveness.
Posted from my HERO200 while waiting for the UPS truck to arrive with a new Optimus.