Personally, unless I was ballistic breaching I would not run a pistol grip only stock. In a defensive or duty shoot, I want to aim. That means looking down the barrel, and through/over the sights to the target. Some people are comfortable firing from the hip, tucked into the chest/ribs, or holding the shotgun forward in both hands and sighting as if it were a pistol. That's fine for them. I want something that is more stable, more consistent, and more precise.
With a conventional stock and standard defensive barrel of 18-20" you're not taking up any more room than what you would occupy with a pistol. You can short stock the shotgun if you need to. There's also the Chuck Taylor method to close your space up.
Folders are nice if you have to work out of a vehicle, or you just have to have a way to stow a shotgun in a very confined space. The problem with folders is that they will frequently not offer a good cheek weld, the locking mechanism can be problematic or wobbly, and they can beat the crap out of you.
The adjustable LOP stocks are good, so long as you can still get a good cheek weld and sight picture with them. The problem is, on Mossbergs you now have a safety manipulation issue and possibly a problem operating the slide release depending on the stock.