it's the combined ratio of rear biased weight and horspower that lets them have the clawing ability through corners.......
also the cars may seem to drift, the whole advantage is that while the 911 appears to be drifting, the grip increases with throttle due to the bias of the weight, more pressure on the rears = more traction. keep in mind that the 911 is more at home at high speeds, where the 944 may be slightly quicker at say an autocross. you really need to put a 911 on a track to fully appreciate it's capabilities, then you will completely understand