I am sort of in the midst of this with my optics as well and thought I'd share a couple of things to consider, and to check my own understanding.
First, exit pupil is calculated by dividing the objective size by the magnification. If there is more to it than that, I am missing it and hope someone clarifies.
Second, it seems accepted that the average maximum pupil size for a "young" person is around 7mm and generally gets smaller as you age, so an exit pupil of of an optic being greater than 7mm is not beneficial.
Third, you need to decide how much magnification you want available and how that will relate to the exit pupil. In other words, do you want to be able to adjust to say 10x or 12x to zero at 100yds, but you hunt and shoot at lower power, even in low light, or do you want to be able to use higher power for shots in all lighting conditions? I often like to use higher power to try to identify any small obstructions (branches, etc.) close to the target, or to pick out details, and this becomes more difficult in low light. Obviously, a higher magnification setting can also cause you to look past obstructions that are very close to you and not the target as well, so there is situational dependence here.
So, a common LPVO of say 1-4X28 would give you a 7mm exit pupil at its max power of 4X, a 3-9X40 would give you a 7mm exit pupil at just under 6X, and a 2.5-10X56 would give you a 7mm exit pupil at 8X.
I consistently see recommendations for large objectives with seemingly not much acknowledgement given to the magnification. In other words, wouldn't a 2.5-10X50 be providing a more than usable exit pupil up until about 7X?
If there are any misunderstandings or generalizations that are too broad here on my part, please correct them. I am trying to firm up my understandings and hope it helps others who are thinking about this.
One other thought...I recently started wearing glasses (again) while hunting. I am struggling to find anything to affirm that the coatings on modern lenses (presumably for blue light) are hindering my low light vision, but it there seems to be an obvious "tint" to my non-transition, "non-tinted" lenses that has led me to think I am wasting my time trying to maximize exit pupil and low light performance if I am wearing glasses that are not allowing the perception of maximum pupil dilation.
