Aguila SSS has a longer 60 grain bullet, which I find does not stabilize well in all guns. Bullet can 'keyhole', etc. Probably does real well in those AR-15 223>22LR conversions with a 1:9 twist.
The Aguila SSS are not any quieter than 38 or 40 grain subsonic loads; at least not when filtered through my hearing aids!
Super Colibris are very quiet, but may not have enough power to make it out of tight or long rifle barrels. I have even had the regular Colibris hang up in both of my 1955 vintage Ruger, flat-top, flat gate Single Six pistols, and they are well broken-in.
If you use Colibris, be very aware of that, and check out the bore after every round for the first half a box. Then, when you are used to how they sound and feel, check your bore again whenever anything doesn't sound or feel right.
CB caps are pretty quiet, and when you get used to the trajectory, they can be quite effective.
Using an 1894 Stevens Favorite (which I have owned since 1957) I have:
-killed a rabbit which was 75 yards away...the bullet didn't break the skin at that range, yet broke the ribs and ruptured the heart.
-knocked a Crow right over, stone cold dead, at 60 yards.
-shot 2 Starlings in a row out of the air as they flew over a family reunion (lots of witnesses); one through the heart, and the second one throught the head.
-shot numerous English Sparrows of of our BlueBird coops at 40 yards.
Don't get me wrong, I miss a lot too. But it's amazing how well that little CB can do!
How close are your nearest neighbors?
Mine are about 250 yards away, and never complain, even when I put 500 rounds of 45ACP through a 1911 pistol on one recent afternoon.
I shoot Muskrats at night here, from the upstairs of my 'garage' with a 17HMR. My wife (a light sleeper) says I never wake her up with them.