Asus Crosshair V Formula is the best mobo for overclocker among 990FX chipset..
Sabertooth designed for durability..and that's why it has 5 years warranty. crosshair just 3 years..
Actually They are both good boards.
The main difference being that the Sabertooth doesn't have the on board sound chips that the Crosshair does.
The Crosshair also overclocks memory better.
And has more USB3.0 (6 vs 4).
Both boards can run crossfire/sli in dual x16, or x16/8/8.
The Crosshair also boasts more overclocking utilities.