I would say gap, whether this is a British sensibility, aesthetic preference or philosophic I'm not sure. In general I am wary of elective bodily embelishment right the way from tattoos to pierced ears. I can see the rationale for some 'repairs' such as cleft palatte / burns surgery, but I don't really know how far this extends to teeth. A friend's Aunt has a sizable gap which is distinctive but not offputting, then again her great niece had a brace, mainly because she had too much tooth and not enough gap... Still, people to public space with fidgitty or 'dead-still'?