iPAD performance

What is the difference in performance between iPhone and iPad (regarding a 3D game)? I mean, I expect the iPad to be far more performing than an iPhone... am i right?

Is there a sort of performance ratio between the two devices? something like: "the iPad is 3 times faster"

No, you're not right. It depends. What iPhone are you talking about? iPhone 4? iPhone 3GS? iPhone 3G? iPhone 2G? The 3GS is likely to be faster, because the screen resolution is 5X less than the iPad. The 3G and 2G iPhones might be slower, because the CPU is a lot slower even if the screen has 5X fewer pixels, but it still depends on what you're doing (using fog on iPad/iPhone 4 kills the framerate, for example). If you're comparing to iPhone 4, then the iPad still has a higher resolution, though not nearly as much compared to the 3GS, so the difference won't be as much. So there is no particular answer aside from "it depends, but probably slower".