Well stars are brighter regardless of the magnification employed. For extended objects yes - bigger aperture's only advantage is more magnification. But for stars, it's brightness. Globs look fuller and brighter.
At the same magnification the image is brighter in the larger aperture, and the eye prefers that in dark sky for galaxies. The calculated contrast is the same, because the surrounding sky is brighter too, but the response of the eye favors the brighter image. This isn't the same as for high surface brightness extended objects such as planets.
At the same magnification globs and open clusters have more resolved stars with larger aperture. Likewise, galaxies and nebulae will have more resolved features with larger aperture.
There is some optimization to be done for seeing different aspects of galaxies, or for seeing the lowest surface brightness targets at all. For the lowest surface brightness extended objects, at some point merely increasing scale with the same aperture becomes counterproductive because the object itself is of such low surface brightness. The surrounding sky might start out in the 21+ mpsas range, but by the time one reaches 1.8mm exit pupil, there is 3 magnitude of dimming. The resultant 24+ mpsas apparent brightness is beginning to approach the ~26 mpsas noise level of the fully dark adapted eye. Further increase in magnification/reduction in exit pupil hurts contrast for the lowest surface brightness features--even though it still improves visibility of the higher surface brightness regions.
The scale needed to resolve very low contrast/very low surface brightness features is large and the appearance is becoming vague/indistinct at threshold. At this point increasing the scale is at or past the point of diminishing returns because the contrast loss becomes a bigger problem for the eye than the benefit of the scale.
I used 1.8mm as illustration because of the ~ 3 magnitude reduction, but I can see some differences in the field with some more uniform low surface brightness galaxies becoming harder to see at 1.8mm vs. 2.2mm (about 2.5 magnitude of dimming.) For very low surface brightness regions 3.2mm exit pupil is more effective (1.7 magnitude of dimming.) And for the very lowest surface brightness aspects/targets in 21.6+ mpsas sky, I have found anywhere from 4mm, 5mm or 6.2mm to be necessary (~1.2, 0.7, and 0.2 magnitude of dimming respectively.)
The opposite is true for galaxies with good surface brightness or good brightening to the center. For them additional scale is helpful even at 1mm exit pupil (4.2 mag dimming.) And some tiny high surface brightness features benefit from even more scale, as on a night of very good seeing I was able to first see indicatons of M87's jet at 1.8mm (278x), moreso at 1.2mm (417x) , becoming confident at 1mm (500x) and certain at 0.8mm (625x). The jet is overlaid on the glow of the central region of M87 which has relatively high surface brightness for a background.
