Sawn-off's are even less practical than a regular shotgun in any realistic combat use. 

We're not in the UK, we're in the post-apocalypse.

Versatility, you have down.

As far as a silent shotgun, you may as well use one of these as well: 
[img]http://static.fjcdn.com/pictures/Senkay.+Silenced+Grenade_6ca3cf_4924856.png[/img] :lol

It's all personal preference at the end of the day. I [b]like[/b] shotguns, especially in post-apocalyptic fiction/games, don't get me wrong on that. I'd just take a bow before I'd take a [b]shotgun[/b].