I ran irons, clone fixed optics, clone red dot, and real red dots.
IMHO if you are someone into making your shot counts, having a good sight is crucial. If you run BB hose, I guess you really don't need any.
Irons are great to a certain extent. They're more affordable and will not fail if you have quality ones. The draw back is the use in low-light and target acquisition time
Fixed Optics are great to see where your bbs go and make your shot adjustment. Anything over 4X in airsoft is excessive
Red dot: They're awesome once you sighted in (PITA in airsoft since the grouping aren't as consistent) I prefer to sight them using the parallel zeroing -this means my dot is always aiming XX distance above point of impact since hopup should've make the bb have a flat trajectory before the rapid drop at the end.
The main draw back for red dot is quality.
Some of the cheapo red dot does not maintain zero at all, some gets completely washout during day time, and some of them when you use make the adjustment they're erratic and does not give you consistent result (1 click may move the dot 1 inch @ 100m, and the next moves 2 inches)
I went through so many clone red dot before biting the bullet and purchase a real Aimpoint. It's one of my best purchase made (I've went through several guns, but the optics stays the same) Benetfit of real (or a really good clone ie Primary Arms) optic; adjustment are consistent, it doesn't washout during daytime, and it maintain zero (I can strip if off to clean my gun and put it backon without noticeable shift in zero)
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