I searched for this comparison but, a bit oddly, failed to find anything pertinent. I'm kinda new here so if it has been covered then please refer me to the source.
I think it is generally accepted that resolution depends primarily on aperture, the larger the lens area, the more light. The question I tried to address is, with respect to viewing only, how big an objective do you need to make a telescope worthwhile over a pair of 50mm binoculars. The calculation is simple - but the answer was a bit surprising and yet may be consistent with practice.
Each of the two binocular-monoculars has an area of pi*625 mm2 , giving a total of pi*1250 mm2.
A single lens with pi*1250 mm2 has a radius of 35 mm, and hence a diameter of 70 mm. Thus, the calculation predicts that a monocular telescope has to have a larger diameter than 70 mm to actually capture more light than a 50mm binocular.
As I see it, eyepieces are irrelevant here since they could be adapted in either case. The obvious unknown is whether pi*1250 mm2 of captured light gives the same resolution if delivered to one eye (telescope) or split between two. I don't know the answer to that - maybe someone here can shed some light (oops...). Its possible that the resolution is greater for two eyes because you are less likely to saturate or vice versa for one eye because the summed light is more likely to be over the threshold for receptor activation.
So is this why commercial telescopes generally have an objective (reflector) >70 mm?