I play the Semi-slav with black, but just thats just by Chance. However, I agree with this comment, and also the fact that far fewer play the Semi-slav, might help you.
Semi-slav is a good tradeoff between solid and dynamic. Not as dynamic as the Grünfeld, but can still give interesting positions.
In my case only if they play the Bg5 line, then you can have a wild game. If they play the Meeran (usually 5.e3) it ends up being more positional,but keeping all pieces and pawns on the board.