I will spare you the details but the conclusion was that aperture rules (if your mount is up to the task).
Hmm - well I piped in at the end of that thread with the thing about pixels vs. arc-seconds - which is very different from aperture rules - and it seemed to be accepted. The thread does come up a lot and it is always a slippery topic - but if you focus on pixels vs. square arc-seconds it makes sense. There is weird stuff about film vs. ccd that confuses things and isn't relevant.
The adu and s/n of nebulosity for a pixel on a given camera just depends on f/ratio of the attached lens. There is a direct trade off of aperture and image scale at a fixed f/ratio and fixed camera, and no magic is involved. Stars behave differently and are much more dependent on aperture.
For the concrete example here - a nebular image with 6" at f/10 and 11" at f/10 will look just as bright (same adu's and per pixel s/n) but the 6" image will be smaller. If you then blow it up, it will have less detail and look noisier. But if you don't blow it up, you will have a nice, wider field and bright image with the 6" vs. the narrow field, but equally bright, 11" image.
So - aperture rules, and f/ratio rules - depending on what you mean.