Quoting: AnandTech: Understanding the iPhone 3GS
"At the same clock speed and with the same L2 cache sizes, ARM shows the Cortex A8 as being able to execute 40% more instructions per second than the ARM11. That’s a generational performance improvement, something that can’t be delivered by clock speed alone, but the comparison is conservative. Cortex A8 designs won’t ship at the same clock speed and cache configurations as ARM11 chips; as far as I can tell, none of the major ARM11 based smartphones even had a L2 cache while Cortex A8 designs are expected to have one."
Excepting the L2 cache (unknown benefit and unknown what the difference is between Moment and Droid) and 3D improvements... a 550 MHz A8 (Droid) ought to perform pretty close to the same as an 800 MHz Arm11 (Moment) according to Arm.
I'm quite curious as to why BGR's experience with the Droid was so much better than other reviewers' experiences with the Moment performance-wise. The most probable explanation I can think of is Android 2.0, such as the new scheduler (same as cyanogenmod's). Another is that the flash/RAM in the Droid could be faster than the Moment's. If you look at the next page of Anand's iPhone 3GS review, it shows some pretty large differences, but the iPhone 3GS had much more RAM and faster flash than the iPhone 3G, which certainly contributed to the gains.
It's because the Droid's chip architecture is far more advanced. It's like comparing a Pentium IV at the same clock speed as a Core-i7, same speed numerically but no comparison in actual performance.
The other major factor is that the Droid has a graphics processing chip built in separate from the main CPU.
These two factors Combined, the Moment has a serious horsepower disadvantage relative to the Droid.