N64 trounces the PS1 in terms of graphics, especially when we consider which one's aged the best. The lack of texture filtering and the jumpy/wobbly vertices and warping textures really make things look bad. Emulators somewhat close the gap on this, but not fully. Even those games that people point out as looking really good on the PS1, they would have looked better on the N64.
Of course, none of this means much of anything when the PS1 library completely destroys the N64 library.