In my opinion the Big Dot is unrivaled for fast target aquisition on pistols and rifles. I have them on all my pistols and most of my ARs (won’t work with Troy BUIS). As you mentioned though you will suffer some at longer ranges because of the width and general shape of the sight. I find I can be just as precise at the expense of increased time to properly aquire the target.
Go with the XS 24/7 sights for the AR15. Dont get the dot because from 100 yards away or more it covers up your entire target. The 24/7 are tritium sights but the front is a stripe tritium. I like the trijicon for the front sight much better.
New member, reading old posts. I have the same plane rear in a dominator A2, and their narrow tritium front. While I don’t use the tritium a lot, the contract in the sight makes it an easy acquisition regardless of the background. The white shows up very well gainst a dark background, and the black outlne around and inside the white shows up well against a light background.
I use X/S sights on all my rifles, and eventually on all my handguns.