Co-witness, flip up front, and rear sights
In this business there is always going to be a considerable amount of research to do unless you are buying based on experience. It’s always a good idea to ask people that are using the equipment or call a manufacturer to get suggestions. We sell a lot of sighting systems from Red dots, crosshair, donut and chevrons. There are different ways to use lines and dots to gather information about range estimations and about different lighting situations. Iron sights have been around a long time and there are, even with iron sights, different sight pictures for different reasons. About 20yrs ago I started seeing more and more optics on AR15s and seeing “glass” on military weapons was just starting to become common.
After about a decade of optics being used, I started to see more and more people putting backup iron sights on their ARs and the optics started trending to zero magnification. All those heavy barreled AR15s with ACOGS were nice, but that platform had it’s disadvantages at close ranges. Magpul has been around for a little over a decade and the Magpul sights are being sold “with” a great many AR15 manufacturers. Its seems their product line, and ingenuity, has been widely accepted. Using red dots or Eotech sights gives you speed but anything with electronics built into it can fail, and having a flip up rear sight isn’t going to add much weight or get in the way of your optic usage. Front sights seem to be somewhat of annoyance to some people when using optics which is why, depending on you AR15 configuration, you can get one “without” the traditional front post sight. Personally, I am not bothered by this and would rather have a fixed front sight rather than have to flip up two sights if an electronic optic goes down.