What's the difference between the Red Dot and Reflex sights?
Solution 1:
Taken from COD Wikia:
The differences between the Reflex Sight and the Red Dot Sight is the Reflex Sight has a slightly larger field of view when looking through the optics.
Personally, I am a bit more comfortable with the reflex sight than with the RDS.
Tactically, there is almost no difference.
Solution 2:
From my experience, Reflex Sights produces more "tunnel vision" compared to Red Dot Sights, which reduces your field of vision slightly when aiming down the sight. But as for gameplay mechanics-wise, they function pretty much the same.