My $0.02 says the galaxy s as a processing unit is slightly better than the older snapdragon. Better optimised, newer (45nm > 60nm) etc. There could very well be processing issues on other chips too. We wont know until someone finds them. Bear in mind however, the Snapdragon chips are likely to be much better optimised for android operating systems - as android is developed on that reference hardware - e.g. nexus one uses a quallcomm snapdragon and gets a massive jump with JIT, froyo. However, droid X, Droid 2 with froyo dont see nearly as high increases in performance.
The GPU is known to be significantly better on the Galaxy S phones. However, its only a matter of time before the next gen snapdragons take the lead again (or at least play catch up)....and somehow I wont be surprised if the subsequent Galaxy S 2 devices retake the lead