I have a grass blade on my fs90. I was very impressed. Earlier somebody compared it to a mower... I would liken it to a bush hog. I prefer to use it in areas that are very overgrown, not so much taller grass. Imo the polycut is better there. It chops up the material into more pieces while the grass blade lays down the grass or weeds in one long piece.
Either attachment its a great way to get more utility out of your equipment.