As the name suggests, enclosed red or reflex sights are closed or encased. They do not allow external elements like water, grease, or dirt to enter easily. Enclosed red dot sights are often designed for more rugged use, which makes them typically more expensive.
Open reflex sights are smaller, lighter, and obstruct the shooter's view less. However, in poor conditions, they may allow excess elements such as dirt, water, or grease to enter more easily. Open red dot sights are often more affordable.
For example, all Aimpoint red dot sights are enclosed. Holosun offers both enclosed and open reflex sights.
In short; if you expect and prepare for the worst-case scenario -> buy an enclosed reflex sight.
If you want a more affordable, lighter, smaller, or competition-designed reflex sight -> buy an open reflex sight.
However, the usage is mostly under normal circumstances in good conditions, so both will serve you well in the long run! Both are suitable for sport shooting and hunting, depending on your personal preferences and needs.
Aawee recommends excellent red dot sight usage videos:
