Here I do some comparison of the existing Shotguns. The Shotgun shotgun, that holiest of X-Com weapons for a while is missing, but it is slightly slower and more accurate than the Black Ops one.
Overall The CAWS is probably the best overall choice, but I lack the ability to buy it yet and it is kind of expensive too. The KS-23M is also a cool one, if somewhat heavy and low on ammo per clip. It has 4 shots per clip and they do weight 4.
The Double Barreled is still useable against some animals too.
UAC Shotgun seems pretty much useless right now. It has the strongest buckshot, but that is about it. It is slower, heavier and lacks other ammo.
In other news, I detect my first Manor. It is barely inside Dragonfly range at least.