Why a 400 speed film choice? There's a phenomenon called "wind". The bigger the camera, the more likely the big bellows will turn it into a shaky kite. Plus potentially longer exposure times with 8x10 due to smaller f-stops being used for equivalent depth of field. Those are logistical factors.
Then there are film personality factors. HP5, for example, can achieve a wonderful etched quality in PMK pyro despite its large grain. TMY 400 is a wonderful all-round performer, with finer grain than most med speed films, yet excellent edge acutance great linearity, and true 400 box speed. And then there Tri-X 320 which some people think is the only film in existence worthy to go with their waxed mustache and black beret, or something like that (I never have quite figured it out) - but I does have its own distinct look.