I shoot better at all ranges with a mini reflex site. I've tested it extensively, back-to-back with otherwise identical guns, and through many drills and even multi-day classes. I'm not a bad or poorly-trained shooter at all. I'm not missing something where the reflex site is serving as a crutch. It is just flat out a better site for me under all circumstances where the sites are used.
I know historically there has been some debate about whether the sites are useful at all in a "real" defensive shooting. The argument that defensive shootings are "likely" to be at close range and therefore inferior sights are preferable doesn't make sense. If you believe that sites are useful at all, then it should be obvious that a good site is better than crummy a one. I have never used adjustable notch-and-blade sites of any type on a handgun that could even come close to the optical ones in visibility, precision, speed, ease of acquisition, and target-focus. For me, they're a huge advantage that I'm not willing to go without. I wasn't always convinced of this, and I tried extensively to prove otherwise -- so I would not have to carry a big red dot or suffer its 'tacticool' aesthetic which is totally incongruous with many other things I do. Bottom line is I cannot justify not having it.
I carry and recommend the Trijicon SRO. The RMR is demonstratably tougher and better at surviving drops, but has a smaller site window. I'm not willing to sake performance for a "what if" contingency -- if I drop the gun, the site could break, but that doesn't mean I can no longer aim the gun. I do not have back-up irons -- again, I opt for the performance of an uncluttered site picture rather than taking a penalty for a "what if." BUIS could make sense on some rifles, but a handgun can be aimed effectively without sites and it can be point-shot.
I have used a dozen different high-end mini red dots: Trijicon, Aimpoint, Leupold, Burris, Vortex, Holosun, Crimson T, Sig, etc. etc. The only good ones I have not used are the Steiner and C-More. I know I'm not the only one though. There's plenty of gun-writer reviews out there that evaluate the top-10 or whatever. Also, I have not tried any of the sub-compact sites for the tiny pistols like shield, 365, 43 etc. If I were buying for myself, the SRO would be my top pick and the ACRO would be the second.
I might even choose a gun around the site. It's that important to me. I would certainly not consider a gun for carry that would not accept one. I've also found the grip is critical to red-dot acquisition. With the right grip, I never miss the dot. With the wrong grips, I end up wiggling the gun around looking for the dot. This is why I would strongly advise to try gun and dot combinations. I don't want to re-train my grip. I expect easy dot acquisition from the get-go. Personally, I use an L-frame Smith with Hogue no-finger-groove grips. I'm not going to recommend pistol and dot combos, but do recognize the ergos are very different between a Sig/Romeo or 1911/DeltaPoint combo and a Glock/RMR. Find what works for you.