This goes against all current “archival wisdom”. Yes, almost all sources would say that the negative is a better source. Sometimes the prints are a better source than the negative, especially on newer material. The process of creating prints often corrects for incorrect exposures, under contrasted images, etc. A lot of the answer to this question lies in the quality of the originals. My recommendation is to scan both and see which one has a)more detail when zoomed in, and b)most closely resembles the actual thing photographed.