Speaker Finish
I think it depends upon the wooden veneer that is chosen to surround the enclosures. Obviously, the type of wooden veener dictates what type of finish should be used.
I prefer dark woods, often with rich grains, rosewood, cherry, mahogany. But, if the veneer is from a light wood, such as beech, oak or maple, then a light finish would be preferrable.
Of course, Black, and a gloss piano black, is always provides a wonderful appearance, so one can't go wrong with that, since it seems to blend in to almost any decor.
Pat