Look at it this way:
Pentium 4 running at 3.4ghz.
Pentium Core2Duo running at 2.2ghz
The C2D runs at a slower clock rate, but the technology allows for everything to run quite faster in comparison to the P4, with all the software being the same.
This might not have helped, I just happen to follow all technology a lot.
The CPU speed comparison isn't as handy as many think it is. Only in the same generation of chips does it apply.
The Android features the same CPU technology as the Palm Pre and iPhone 3GS. This chip is far faster than other chips prior, and a 550mhz ARM Cortex 8 CPU (the type in the Droid, Palm Pre, iPhone 3GS), can run quite a bit faster than even the 800mhz ARM11 in the Samsung Galaxy i5700. The ARM C8 is a far faster CPU design than the very common ARM11 CPU design found in nearly every other smartphone.
Suffice it to say: the only thing slower in the Droid is the clock rate, in comparison to other phones. It doesn't matter the differences of CPU usage between Android and Windows Mobile, it's simply the CPU's clock rate isn't a valid comparison point.
Hope that helped.