If you're anything like me, I usually keep my speakers for quite some time. Therefore, I need a finish that travels well and matches the furniture and "decor" of any place I move into. So, to answer the question, I usually tend to choose a black finish. Black may not be the most visually pleasing, but it is, in my opinion, the most practical.
Nonethelss, I do admit that I have quite a soft spot for rosewood. It certainly is the most "expensive-looking" finish, IMO.