the way it works is that Pentiums are built for clock speed, while AMDs are built for power.
Whats really amazing is that the equivelant to a 2.2Ghz P4 chip is an AMD 1.67Ghz chip. In my experiences, AMDs run cleaner, Pentiums are better to brag about, but if you want the raw performance and dont care about bragging rights, AMD is always the way to go.
I would say the AMD 2600 is faster than the P4 2.6. Much faster.
While it would run at a lower speed, it would run better and its been proven in every single test. AMD whips Pentium for gaming performance.