I'm one Vancouver fan who has been questioning Horvat for years.
To me he is best described as heavy player. This helps in the physical department and makes him rough to move away from the net allowing him to tip pucks. He can also bull rush the puck to the net and ward off people trying to vend him off. Also he has power in the face off circle - he can get low and hold off the other player as he wins the puck. These to me are the his three best qualities - tipping and moving pucks from in close, building up speed and barging to the net and face offs.
The other side of this, however, is that Horvat is far from agile or especially quick. He has very clunky first step and pivots poorly. Often he can't hold his balance and over rotates and ends up spinning around. This makes changes in direction slow and limits his ability to react quickly defensively and limits his coverage. In fact, he is -65 career-wise. (of course some of this due to playing on a team as bad defensively as the Canucks). For some reason he was played on the PK and this has contributed to historically bad numbers for the PK in Vancouver. Horvat, defensively will not get pressure on the puck ever. Plays sort of zone defense and hangs out in the middle of the defensive zone.
The other problem is that he is not particularly good in transition because of his skating issues. Nor is he a play driver although he can make the quick smart pass around the net. But he he is not the type of player that packs the puck around the offensive zone looking to distribute.
He is like a lot of good offensive players who may not skate well, but skate well enough and are smart enough to get to the net and do something with the puck.
Overall, I don't think (and I've argued this for years) he is not a great two way player. But he is strong and good in tight places. If plays in the 2C spot and gets the right match ups, he can produce.
Not that much different in style than a player like Lee.