Originally Posted by HellRanger
And if I'm not mistaking the what you refer to as a "CQB sight" and a "Marksman sight"... Aren't they actual "night" and "day" sights? In low light condition, you would be using the one with the big opening and in day light you woudl use the smaller one. Fire using the night sight during the day and you grouping will be shitty (With real steel mind you). But I might be wrong...
The original poster is correct. The smaller peep is for higher accuracy (for both airsoft and RS). I've used the smaller peep sight during the day, and it works wonders for accuracy (assuming the gun is up for it).
As for night, neither are really visible to me, so both are useless.