Maxwell Everett said:
It is interesting to note that the large area to the left and the small area to the right in the ENT image does conform somewhat to where extra image area would be if the 35mm film from "Ménage à Troi" wasn't hard matted in-camera.
Perhaps director Rob Legato (one of TNG's VFX Supervisors) decided that for his episode he wasn't going to hard-matte the image in-camera.
But if that is the case -- why did they also have to crop the top and bottom of the image for ENT?
Another possibility was that this practice of hard-matting in-camera was inconsistent during TNG's run and simply resulted in a stroke of good luck for this particular shot being used in ENT?
It was an occasional practice to shoot shots requiring later optical work in VistaVision on TNG, that way there'd be extra image on 'either side' so that an electronic pan&scan type move could be introduced into an otherwise static shot. Rob Legato started doing this on LAST OUTPOST (panning off Riker to show some dry ice and model mountains, I think), and used it plenty of other times as well.
It is cheaper than motion control, and this technique has even been used on feature films such as THE SIXTH DAY, as a way to get movement into a static camera setup requiring visual trickery.