You should make sure that your new PowerBook has enough memory (1GB at least). You should also read this article
. It looks like CS2 uses a different memory management than CS.
Both PowerBooks share the same processor and same amount of processor cache. The new 1.67 should outperform the old 1.33 - provided you have the same version of Photoshop and same amount of RAM (hard drive perfomance can also play a role) running on both machines.