Digital should be the better for either one because both can be normalized to a normal exposure, in which case over should still be more accurate (assuming a static scene). With film, you open the shutter and then allow light to hit the single piece of film, which makes up your full data for that image. Digital could record time data with the light data and essentially keep a record of the full exposure, which can then be averaged and normalized to the length of the exposure.

As long as no pixels get blown out by the exposure, linearly scaling brightness would handle the normalization. Though one of those "take 30 pictures real quick" would also work if you average them together, maybe add a little positional correction if the first frame and last frame are far enough apart that the spacecraft has moved significantly in that time.