Maximum pinhole resolution is more a function of pinhole size than format size. Therefore, wide angle pinholes for a given size can yield sharper images in the center of a photo than can longer pinholes. As I recall, the maximum line pair resolution of a pinhole of optimum size is slightly better than the pinhole diameter. This is counterintuitive, but diffraction limited optics don't behave according to simple logic. Nor do pinhole photographers!