Early Benchmarks: iPad > iPhone 4 > iPhone 3GS
The giant iPhone is still the fastest one.
We all know that the new iPhone 4 runs on the same A4 package-on-package, err, package as the iPad. It's nice little ARM and PowerVR combo chip that works quite well the iOS.
Apple never disclosed the clock speed of the A4 in the iPhone 4, which means that it could be running slower than the 1GHz model in the iPad. That would make sense as battery life is a more critical factor for a phone.
Early benchmarks, as shown by MacRumors, between the devices seem to show that the iPhone 4 is indeed a bit slower than the 1GHz iPad, but still faster than the 600MHz Cortex A8 iPhone 3GS.
For those pondering how much faster the iPhone 4 is over the 3GS, Geekbench for iOS4 show that the new phone is 31 percent faster than last year's model.