His flaws are obvious if you watch anything more than his drives to the net. He is a very poor passer. He doesn't anticipate passes, he is inaccurate and he throws the puck hard so it is difficult for his teammate to control. He even entirely misses obvious passing opportunities. He has a lot of David Booth drive no matter what in him and it detracts from other elements of his game. I really question how his game will come together because it is far from complete. I would agree with Pierre that he is going to need a center to spoon-feed him one on one opportunities on the rush and I would add that he hasn't shown hints of any skills beyond that.
As for Bo, any 3rd line C projection is bunk. He may play that to start off but the guy has top line talent. He scores NHL style goals and isn't bothered by contact in the least. He is extremely intelligent on the ice, both offensively and defensively. There is a variety to his offensive decisions that shows a high level of creativity. He is constantly anticipating the play.
You shouldn't be comparing prospects statistically, but if you need one thing to separate Horvat from Gaunce it is the fluidity with which he moves from one play to the next. He plays faster than almost everyone on the ice and that isn't talking about his skating speed.