AR-15 peep sight

[capstan]

My Ar has 2 rear peep sights 1 is larger for up to 200 yards and the other smaller one for over 200 yards (I think that's what the manual says)
It seems like the larger peep would be harder to get a deadcenter fix on the front sight. Is there any reason not to use the smaller peep sight exclusively for more accuracy in centering the front sight. Or am I missing something?

[TooTech]

Smaller peep aperature lets less light get to your eye. Low light visibility suffers as a consequence. Also easier to find your aiming point with the larger aperature.