I'm pretty eclectic and common sense when it comes to tactics for night home defense, with a few a key concepts in mind.
1. The odds are that someone entering your house will be less well low light adapted than you are, and you will know the layout of your house while the intruder will not.
Consequently, you have an advantage that you'll lose when you start using a light, and yet way too many people want to turn on the lights or run around flashing their tactical flashlight to level the playing field to their own disadvantage.
A light is also very likely to draw fire if the intruder is armed and intends to shoot, so a brief activation via a momentary switch is your best bet. I'm also in agreement that having a really bright tactical light just because you can is a really bad idea. You are not going to "blind" an intruder, but too much light will further impair your night vision and is way more light than your dark adapted eyes need for target identification. 100-200 lumens is plenty, and if you choose wisely, you can find a light that offers a few levels of output that can be set separately from the momentary switch. In other words, you want a light with a momentary switch that can be set to turn on at a low level of brightness, around 100-200 lumens.
With that in mind, a light on a personal defense carbine isn't a bad idea, but it needs to be used very sparingly and only when you absolutely need to identify a target you are about to shoot. For example, you probably do not want to shoot your teenage daughter's boyfriend who came in the back door she left unlocked. Or maybe you do. Either way a light can allow you to properly identify the target before you shoot it.
2. I'm a big believer is shooting instinctively, with both eyes open looking over the weapon.
For example, way back in the day we were taught to fire at night with an M16A1, both eyes open looking over the carry handle. At social shooting distances it was plenty accurate.
In that regard, I'm in agreement that iron sights are sufficient - if you practice enough to get comfortable and confident with that approach.
3. I'm not a fan of short barrels in a home defense carbine.
For 9mm Luger purposes 8.3" is a sweet spot, losing only 125 fps or so compared to a 16" carbine barrel, and only being about twice as loud at 120 dB, compared to 117dB for the 16" barrel.
However, the downsides of the short barrel are potentially more muzzle flash, and much more importantly a greater potential for a user to get one or more fingers in front of the barrel when firing under extreme stress. There's never a good time to blow your own fingers off, but doing it while being shot at is worse than most.
Consequently I added a flash can and a free float tube to give a little more real estate to hold the weapon. The increase in weight is minimal, but length might be an issue depending on how you store it.
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With all that said, I also like my personal defense carbine to be reasonably flexible, capable of engaging targets at both short and long range with no change in configuration.
Below is my PDW, a 9mm AR-15 with a light and a Burris 332.
The Burris 332 is a reflex sight so it has a reticle even if the unit is off or the batteries are dead, the batteries just illuminate the reticle. The retical is also a modified donut, and that combined with the low magnification means it's easy to use at short range with both eyes open and just looking at the target.
Your non dominant eye will clearly see the target and your dominant eye will impose the reticle on the target, even if it is magnified slightly, or slightly out of focus.
In bright light with the black reticle, or in the dark if the reticle is illuminated, you also get the same effect as a red dot sight for the same reasons the original Single Point occluded eye sight worked.
At the other extreme, the Burris 332 and the dots in the lower half of the reticle (see above) will also let me accurately engage people sized targets to 200 yards with the 9mm 115 gr XTPs I use in it, making it a very useful truck gun as well as a home defense weapon.
The light is mounted so that the momentary switch can be easily reached and activated by the thumb on the week hand as it grips the forend. The light itself has 4 separate power settings and the second setting works perfect for use at night. I also have a separate switch that can be used instead, and attached to the weapon, but I have not found it offers any real advantage. It's easier to remove the light during the day when I don't need it without the separate switch.