2900 XT VS 8800 Ultra question

Ok, don't flame me for this, its just a question:

I was going some research on these two cards; the ATI 2900XT and the 8800Ultra, and I check futuremarks website for comparisons as well as Toms benchmarks for comparisons and I was wondering why there was such a huge difference.

On Futuremarks ORB (Online ResultBrowser) the 2900XT compares really well to the 8800Ultra, and sometimes even beats it in crossfire configuration. but on other benchies I find that the 8800 actually does alot better then the 2900. Why is this?

But thats the thing, even in Toms benchies when their using 3Dmark06, the 8800ultra beats the 2900XT by alot. Except in systems listed on 3Dmarks website (which are more real world IMO then the test machines during benchies) the opposite is happening.

It's called a synthetic benchmark for a reason; real world games will stress different parts of the GPU more than benchmarks which basically test only certain features. If you were to increase the resolution to 2560x1600 and enable 16xAA and 16xAF on both cards, I'd bet the HD 2900XT wouldn't be nearly as close.

Thats what I'm thinking.
I wasn't trying to compare game/other performance with synthetic but compare synthetic vs synthetic and something wasn't adding up. I guess a lot of people might of misunderstood me.