@Club Sandwich Thanks for all the insight, really helped me know what to look for with doing my research.
you're welcome. it's worth noting that i typically don't use an optic other than shooting farther than 300 meters, sometimes shorter if doing initial zeroing or using something short ranged (pistol, shotgun, et c). a rifleman should be able to achieve repeated strikes on target at out to 300 meters unsupported and 600 meters with supported, aimed slow fire. all an optic does is add complexity and weight to your rifle for the benefit of seeing at a greater distance. in highly mobile situations, a red dot is helpful to draw the eye and center the point of aim, especially when moving and shooting at close range.
within that frame of reference, the differences between optics are highly muted. the optic, like any other accessory you are purchasing, should be used to enhance your shooting when you are being limited by the rifle, rather than your personal ability. if nothing else, correct, quality glasses, and a focus on fundamental rifle skills, professional training (or amateur training with information from professionals), and a lot of regular practice will do the average shooter far more good than purchasing an optic and depending on it to "do the work" of sighting a target for them.
it's a fine distinction, but one worth keeping in mind.
Before I set my decision in stone, I just wanted to get a final comparison of the holosun 503G vs the aimpoint pro and a wild card: sig romeo 7. The aimpoint is surely a better built product, but besides "overall quality", is there any specifics with the function of the aimpoint over the holosun? edge distortion (is this parallax?), etc?
the Romeo 7 is a more annoying to use Aimpoint PRO that uses a more convenient battery and has a unique mount. the HS503 is much lighter weight than both, and while it's more of a lighter-use optic, it can carry it's own weight well enough and is more durable than the average recreational shooter will give it credit for. most people using it aren't conducting air assaults, breaching buildings, or anything like that, and being thrown in a truck bed or carelessly dropped on the ground is a pretty low bar to meet. note that some very cheap optics and even a few expensive ones do not meet even that bar.
you will never notice the edge distortion unless you are specifically looking for it. only holographic weapon sights, occluded, or collimator sights lack edge distortion completely (where quality glass is used). parallax is the movement of the reticle in relation to it's superposition over the target at distance, from the viewpoint of the eye. as the eye moves in the eye box (your head moving or shifting position slightly) the reticle may seem to also shift position. this effect is parallax and is related to how a lens works to bend light through it. higher quality lenses, and lens design will minimize this. most "tube" optics will not have parallax within their eye box, but will experience occlusion of the reticle completely if the eye is outside of the eye box.
reflex sights, or "open" sights have a very large eye box (hence field of view as well), but will be more prone to parallax. a true prism-based holographic sight has no parallax at all due to how the reticle is generated. parallax is a geometric illusion and while it can throw off aim, it isn't real and can be trained to overcome, or you can choose optics that minimize the effect.
