Reflex sights, red dots and clarity and precision
Sounds like a wordy subject line but so many people find out the hard way that certain levels of eyesight mean you can’t see so well with some of the modern optics. Eye relief is a big one for those that don’t like some of the Trijicon ACOGS because you do have to put your eye pretty close to get a sight picture while optics like the TA11H-G give you a little more eye relief but its a much larger platform to mount. The Aimpoint Micro T1 got some negative responses recently because according to our customer that the red dot sight looked broken 
or flared, we informed them that this isn’t a defect in the optic, it actually has to do with how the operator’s eyes view the red dot. Sometimes it pays to walk in a store and look through and optic before dropping $600 bucks on one.
Recently I learned a lot about the differences between the Aimpoint, Bushnell, Eotech and Trijicon RMR sights and have pretty good knowledge on helping customers narrow down what they really should consider. Knowing the dot size you want to go with is a good way to narrow your product options and knowing what type of battery life you are asking for. The Trijicon RMR sights have been constantly expanding and are used on handguns as much as Remington 870 and Mossberg 500 shotguns as well as secondary sights on AR15s. Sure they are expensive but giving the clarity, battery life, and far more precise red dots than many other manufacturers, you may find it actually useable when the other product you were looking for is not compatible.