The analysis was correct: the iPhone 3GS graphical abilities are significantly better than the iPhone 3G. Here's how much better, according to OpenGL benchmarks:

* The CPU performance is Faster by 40-70%
* The fillrate* is 3x to 4x higher
* Texture effects and filters are about 10x faster

Keep in mind that it's also running OpenGL1.x on the benchmark test, and iPhone 3GS can run OpenGL 2.x. The upside is that when games do get optimized or developed for OpenGL 2.x, that's when your old phone will no longer be able to play them, or at least play them with better graphics. It's pretty obvious once you play with the phone that it's rendering your old games much faster, but it's good to get it in quantitative form. [glbenchmark via Extremetech via Ubergizmo]