Something to consider: I mounted a 4MOA dot optic on my 300AAC PDW destined for use in my work vehicle. Everything seemed fine for initial short range zero. A couple days ago I was doing a zero check and coarse accuracy eval when I realized not only could I not aim at the 2" target sticker @ 100 yards, I could only roughly aim at the 18" cardboard backer due to the light/shadow combination at the time. More thought and testing will be required.
I have a Holosun on mine. It works fine for what it is, a short range, pistol caliber carbine. I would use this from 75 yds to 10 yds. after all, it is a 9mm pistol round, and using it for extended range shooting is not what it is designed for (IMHO)
I love my Ruger Carbine, lots of fun to shoot and accurate. I was actually pretty accurate with the iron sites but had planned optics. I went with the Romeo 5, got it for $99 last Christmas. It works well and a choice of mounts, I chose to set up higher so it will co-witness. I then put a flashlight/strobe with green dot on the front lower rail. At my indoor range, 50 ft I knock the center out using iron, red dot and green dot.
In light of the current social situations (political, crime, ultra-conservatives, ultra-liberals, fascists, & anti-fascists, etc), I broke down and bought a Rurger AR556 for myself and a PC9 for the wife (BTW: We are both college educated, middle of the road, semi conservative, & middle-class). We are also a couple of cantankerous old farts with no delusions of surviving even a short-term firefight. Just to forestall anyone asking "WHY": My maternal side is Irish. That's enough reason!
That being said, I put a Tru-Glo 1-6x lighted reticle on my AR556 (2 colors) and a lighted dot (2 colors on her PC9. I like both and would be comfortable with either (best of both worlds?) on the PC9. The red dot is slightly faster.\
Best solution... Get a red dot (I prefer prism, especially for tired eyes) and add a 3X multiplier for when you need it.
Way better eye relief than a scope, and you just flip over multiplier when you want to push distance.
My suggested pair? Obviously Primary Arms with ACSS etched reticle for 9mm.
I can highly recommend the Burris 332 prism 'scope' IF you can get it mounted for proper eye relief. This is/might be a problem with some platforms such as the AR pistol since it's hard to justify an optic with a 3-4" eye relief on a 'handgun'. I've used this optic on an AR carbine and it's certainly a viable alternative although not a 'both eyes open' solution like a plain dot optic.
I slapped a cheap red dot on mine because I can't justify spending money on a good one. Works well enough. My carbine was also used and the previous owner had removed the iron sights so I had to put something on it.