Yeah but it's [Hummingbird] been customized to perform better.
Think of it as a 1.1GHz Cortex A8 with SGX540 (drools)

now if you think that doesn't matter, compare it to the Snapdragon.
This is a completely modified SoC (not an ARM Cortex A8) and it performs below a 1GHz Cortex A8's standard (I think more at 880MHz). Also it combines a much slower Adreno 200 GPU (comparable to a SGX530).

So the Nexus One and Samsung Galaxy S are actually on the opposing sides of the Cortex A8 performance, but with Android's java implementation, both chips perform quite close (probably cause HTC's software implementation is better).