I'm not so sure that's true. The top of the line Maximus series uses the same (8+4+2) phases as the Sabertooth. If you listen to the Asus rep the systems with less phases have larger chokes that use more amperage but never says if one system is better than the other.
This info is at 1:00:05 in this very long video:
ASUS Z77 Motherboard Overview and Features - PC Perspective - YouTube
All the Asus boards OC well so you should concentrate on the features you need and want.
Just read the Asus MB reviews to see this is true.