Dining rooms like Living Rooms are about ambience. These rooms are social centers, where we meet family and friends, where we go to think, talk, slow down and relax. Mirrors are purely decorative, employed for effect as pure design. As such a convex mirrors reciprocates in all respects when set against this condition.
I’ve read in the marketing material for some companies that convex mirrors were used historically as a device for the butler to keep a discreet eye on the table while working at the sideboard. Hard to believe. Don’t acquire a convex mirror to be practical. Have it because it will make your room feel special.