I know a lot of peoople will disagree with this but I reckon that the eastern forehand is better than the semi-western or western.
1 - It is more natural and easier to hit the ball as it matches the palm of your hand.
2 - It is more versatile.
3 - Studies have shown less wrist injuries associated with people who use the eastern over the other two.
4 - It is possible to generate just as much topspin and power.
5 - The most successful player of all time (Federer) uses an eastern. The second most successful (Sampras) used an eastern.
This is just my opinion of course but I win more matches when I use the eastern than the semi-western and I don't think that the semi-western should be taught to juniors as "the only forehand grip" over the others.
So what do you all think?