this one disagrees with the first one out by tweaktown early on with immature drivers, but agrees with another i've seen translated from swedish.
The bottlenecking has nothing to do with drivers. New drivers cannot decrease pcie bus traffic. The difference lies in the settings the two use.
See this, for example:http://www.legionhardware.com/document.php?id=761&p=2
Legionshardware use DX9, High quality, AA off, AF off.http://www.tweaktown.com/articles/1472/7/page_7_benchmarks_crysis/index.html
Tweaktown use DX10, Very High quality, AA/AF on.
More intensive graphics settings will stress the pcie bus and thus increase the difference seen. Both benchmarks are valid, just at different settings.
Although between the two, I would say Tweaktown's choice of using higher settings get more useful results. Crossfire setups are considered high end. Few people with setups such as dual 4870 are willing to turn off AA and AF completely. They paid so much for 2 cards so they can see the eyecandy. Turning them off defeats the purpose of crossfire.