Horvat is more of a natural, in my opinion. I haven't seen as much of Gaunce, but the biggest factor is the transitional play and skating. That's what sets them apart. Bo is more natural, or instinctual than Gaunce in the sense that he is more able to create something out of nothing. Fast break scoring, and breaking out of his own zone is a big strong suit.
Gaunce is very solid in the offensive zone in terms of facilitating a play, but Horvat is more likely to take over a game. Gaunce is more of a player that lets the game come to him.