The main difference is quite obvious -- for the same price as a 16GB iPhone3G S you only get a 8GB Palm Pre. In comparison, the current generation 8GB iPhone 3G dropped in price to $99, going after Pre's lower capacity storage.
For just $100 more than the Palm Pre (that is if you get your ) you can get a top-notch iPhone 3G S with a whopping 32GB of storage (four times more than the Pre).
However, the Palm Pre offers a better deal against the iPhone 3G S when it comes to the data plan. AT&T did not reduce its iPhone tariffs, so the Pre on Sprint still offers more for the buck when it comes to data, voice and text plans.
Both the Pre and iPhone 3Gs have a 3-megapixel cameras, however there are some major differences in features. The Pre's camera has an LED flash, but no autofocus, video recording or editing capabilities. You also cannot adjust white balance or exposure.
Apple did not throw in a flash for this generation, but the iPhone 3Gs brand new camera gets some pretty nifty features nonetheless. You can now control focus either by tapping on the screen or using the autofocus feature.