I do not like this trait, especially because of the second text section in the screenshot and given the general variability of the black pigment in the two Metellina. As one can see, Raffaele' s specimen lacks dark pigmentation altogether! I should check my darker segmentata females for this though. Otherwise, I also tend towards segmentata mostly because of time of year (even if I have found maature mengei males in autumn), rest of colour scheme, epigyne silhouette (even if latter is a bit hard to discern, I think that the larger epigynal plate depressions in mengei would look differently on the photos.
Simeon