To me anything that is designed to run at that speed will beat anything you have to 'jail break' to run at that speed.

The desire / nexus and other 1Ghz phones are designed for it, the N900 isn't designed for that, it might let you but it isn't the same thing.

I can only compare the HTC Desire and my under performing N900 @ 600Mhz, and in every way the 1GHZ is faster, but it is software related and buggy OS, not a CPU issue that slows the N900 down. Making it faster still leaves you with the OS.