I really don't know WHAT I need, which is precisely why I asked here in the first place.
OK, I'll go down the list then:
1. Multiple Apertures - originally the rear sight of the M16 was not elevation adjustable and the two different apertures also were set to two different zeros - one for short range and one for longer range.
The advantages of the multile apertures are that a larger diameter aperture is handy for more dynamic shooting at close ranges (you or target or both are moving). The larger aperture is also useful in low light, since the small aperture can cut down light enough to make it difficult to see the target or front sight post in dim lighting. The smaller aperture is helpful for more precise shooting.
2. Same Plane Apertures - the A1 and A2 apertures are not on the same plane. That is, they both change the zero when you flip the aperture. For example, point of impact can change 4-7" at 100yds when flipping between the small and large apertures on an A2 sighted carbine. If you find this more of a bug than a feature, then a same plane aperture eliminates this problem.
3. Elevation Adjustable Rear - .223 is a pretty flat shooting cartridge. This is basically only useful if you plan to shoot past 300m using iron sights.
4. Folding Sight - do you want the rear sight to be mounted on the rifle, even if another primary optic is already mounted? A folding rear sight can be mounted underneath a magnified optic or in conjunction with a magnifier/red dot or night-vision/red dot without interfering. On the flip side, if you don't need magnification and want a rugged back up sight system that is immediately available if the optic fails, then a fixed rear sight might be more desirable (You can also use some optics like big ghost ring sights in the event of an optic failure)
5. Spring Loaded - You push a button/flip a lever and the folding sight springs into place automatically instead of you having to push it into position. A neat feature; but one of debateable value. It also limits your options in folding sights quite a bit; but it deploys really fast
Like anything else, just figure out what features you want/need first and then you can start the process of figuring out which of the twenty-dozen AR sights offers the best combination of features you want, quality and a price you can afford.
