For defensive running forehand slice, the continental gives you more time as you can hit the ball when it's behind you and still get it back.
For approach shots, returns, or change of pace, I've started using the Eastern Forehand as well. My continental slice tended to be a floater that threw off my opponent with wicked sidespin, but this was not effective for approach shots, and it tends to be inconsistent.
The Eastern forehand slice is more biting and gives the opponent less time to prepare..I also used it as an alternative to trying to crush weak second serves, instead slicing the ball directly at the feet of the server and charging the net...more often then not resulted in bad footwork and a weak return or error. When you are dealing with rec players like me, often times hitting right at them is more effective than anything.
3.5 player. Equipment: Prince Original Graphite OS, Tourna Big Hitter Blue