Hm, i´m simply not interested in an Arata vs Chihaya-match. If only because those two don´t feel like rivals to me. A match between them would be ... cute. Nostalgic. nice. "neat". But it´s more something that should happen in the last episode of the series, like when Goku challenged the re-born Boo aka Oob.
Meanwhile, Arata and Taichi aren´t thick friends. They´d go at each other as true opponents/enemies (assuming both are of similar skill). Considering there´s also somewhat of a love plot surrounding the triplette of Chihaya, Taichi and Arata, a match between the two male choices would be all the more interesting.