I took a look at the original manga (Hori-san to Miyamura-kun) and I gotta say I like this version (Horimiya) better. Putting the drawing aside, what I like the most about it is that it's mainly told from Hori's POV. I find this works better than having Miyamura as POV character, like in the original, since it gives it a more unique flair. When this story is told from Miya's POV it feels like your run of the mile shounen romance, but when it's told from Hori's POV it's like a blend between shounen and shoujo, which is extremity cool.
Too bad the OVA was based on the original. It should have been based on this one.