The shield is supposed to be there for cooling, but people say the difference is negligible if the casing is well ventilated. However, the Sabertooth does come with a 5 year warranty instead of the 3 years for the P8P67 Pro. On the other hand the P8P67 Pro seems to have on-board bluetooth.
If you prefer the look or want the 2 extra year of warranty, go for the Sabertooth. If you want to save some $$$ or want the bluetooth, then go for the Pro.