My hat goes off to any cinematographer who can shoot well in B/W. Ideally, one needs to be able to "see" in B/W in order to shoot it properly. Lighting, costume, makeup, set design, etc. should all be executed strictly in accordance with tonal quality; it's a very specific discipline.
That said, I think the easier route technically would be to shoot in color and convert to B/W in post. There are two advantages to this. First, if you change your mind later you aren't stuck with it. Second, my experience is most labs only occasionally develop B/W film. Since the chemistry is different they often will wait until they have a sufficient batch of work to make it worth their while. (Admittedly, though, there could be a lab somewhere that specializes in it.)
On the other hand, B/W negative cinematography, if done well, has such a splendid contrast range that can't really be duplicated in color. Color film converted to B/W seems to often have a slightly muddy look to it, though you might be able to correct a lot of that these days with FCP.