A pistol caliber long gun is better than a 5.56????????? In what way? 9mm typically has much more penetration than a 5.56, and the 9mm isn't comparible at all to the damage 5.56 will do. Pistol rounds of any caliber cause what is called crushing wounds, basically meaning that the temporary cavity made by the round (FMJ or expanding) is almost non existant. The primary wounding mechanism is the permanent cavity that is caused by the tissue that the round displaces when it travels through flesh. With high powered rifle rounds, there is a substantial temporary cavity that is the primary wounding mechanism due to the fragmentation of the round. What occurs is the tissue surrounding the fragmenting bullet is torn, ripped, stretched and basically destroyed. The shotgun with 00 buck has basically the same wounding mechanism as the pistol, the temporary cavity. There will be several .32 caliber projectiles creating a permanent cavity through flesh. The buckshot does not have enough velocity to fragment or cause a significant temporary cavity.
Here's some illustrations of the rifle rounds wounding mechanisms taken from 10-8:
(the shaded area is the permanent cavity)
There is a good reason that the shotgun and SMG have fallen out of favor with many of our best SWAT/.mil people as primary weapons. There are simply better tools for the job.
As to the noise, get one of these:
Since fragmentation is the key to the wounding mechanism of the high powered rifle, my rifle and silencer pictured above are chambered for 6.8mm. I have opted to only practice with 5.56 because ammo is plentiful and cheap and I typically shoot in excess of 1,000 rds a month. While this is a fairly expensive setup to use for home defense, there are much cheaper ways to obtain something that will perform similarly. Also, I don't like putting a price tag on me and my families safety, I simply want the best tool I can find to defend myself.
Different strokes for different folks, but I use my 5 shotguns to kill birds, not anything else.