To answer this question first it is important to understand that these two sighting systems have different purposes.
An iron sighting system, or sighting posts, is a traditional system that involved lining up a rear sight or ring and a front post in order to place your rounds on target. With the right training, these systems can be quite accurate out to a couple hundred yards (2 football fields).
The benefit in the iron sighting system is that it is unlikely to fail. It has no batteries, few or no moving parts, and with tritium technology it can even glow in the dark. The down-side to iron sighting is in its major shortcoming: distance.
When you have an iron sight system, you have 3 things to look at: rear sight, front sight, and target. But your eyes can only focus on one visual distance at a time, leaving the other two object fuzzy or out of focus. Imagine putting a balloon at the end of a football field and trying to shoot it with your pistol. What will you bring into focus? The balloon? Your rear sight? Your front sight? You can’t do all three, and ideally you should be focusing on the front-sight only; which mean your balloon is just a fuzzy blur in the distance.
That is where the red-dot optic or reflex optic comes into play. It is a piece of glass with an LED light reflected in it, which gives the appears of a bright red dot floating in the middle of the glass window. The optic is designed so that in order to bring the illuminated dot, reticle, circle, or chevron into focus you must look into the distance. If you try to focus directly on the illuminated dot, it will appear fuzzy.
Now, with your optic, you can look through the glass directly at your balloon in the end-zone and bring it into sharp focus (assuming our eyes are decent) and your dot will hover in the glass superimposed over your target.
Sounds like a miracle, right? Most military and law enforcement groups are transitioning to firearms with optics. However, they do have weaknesses.
Optics tend to be battery powered, with only a few having solar backups or fiber optic lighting systems. When the battery dies, you can’t just aim through the glass (believe us, we’ve tried).
Glass can break. Electronics can be damaged. The more money you spend, the more durable the optic. Optics are not cheap.
Because of the nature of the human brain, lasers and red-dots can introduce an additional challenge when learning to shoot. All of us, no matter how steely and ice-cold our nerves are, have a certain amount of shake from the electricity in our muscles when we are holding a gun and firing. With iron sights, that vibration is nearly imperceptible. But with a laser or a red-dot, suddenly it is like having a cat-toy dancing in front of your vision. You can see every twitch, dance, and shake that your hands make as you try to steady your gun. For most shooters, this proves to be a major hurdle — since the distraction this plays on your brain will cause you to anticipate your shots and “flinch” as you press the trigger.
What we recommend:
Learn on irons first. Take classes, get proficient. When you are ready, buy a decent red-dot and use BOTH. When you can still see your iron sights through the glass of your optic, this is called COWITNESS, and it is highly recommended for those rare situations in which your optic might fail.