iClarified reports that based on evidence found within the iOS 4.3 firmware, the iPhone 5 is likely to have the same dual-core A5 processor as the iPad 2. This is not at all shocking; last year, the iPhone 4 launched with the same A4 processor that debuted in the original iPad.
The iPad 2 is showing benchmark results well over 150 percent better than the original iPad, and we can probably expect the same situation for the iPhone 5. This means that, at least in terms of raw computing performance, the next-gen iPhone may be even more powerful than the first iPad. In terms of how fast the device will "feel," that's anyone's guess -- but it's worth noting that early reviews of the iPad 2 say it feels at least twice as fast as the model it replaces.