IMO, Any caliber is better than nothing. That said, If I had a choice, say in my Apt, it's gonna be a 12 Gauge. Would I use a .22 if I had to? Absolutely! In regards to "flash" I'd suggest taking a course with your AR, that involves limited/no light. I shot my Noveske in the dark & couldn't believe how effective the Hider was!!! NO problem with vision, or follow up shots. Rifles, Hiders & Ammo can & will vary.
Yes I took the pic, no I didn't go swimming!