So Gunnut17... this is your short list of HD guns you'd like to have?
Are you asking what others would like, or what others actually own and utilize for the purpose?
Rather than responding to your question, how about I ask you... why do you want the guns you've listed? Just curious ya' know.
These are guns that I'd like to have for HD, didn't mean to confuse anyone.
So, on to your question, I picked the Saiga because it's high-capacity for a shotgun, 10 to 30 rounds, and semi-auto, so missing your first shot as big a problem as with a pump gun. But if it weren't able to cycle low recoil rounds, the Mossberg is a compact gun in cruiser configuration, and I like the think the tang safety is easier than the button safety on the Remington 870.
The Five-Seven because it has a 20 round mag which can be upgraded to 30 rounds, the flashlight illuminates the way for you and makes the gun front heavy, reducing muzzle rise, and that combined with the red dot will make target acquisition that much easier. The USP is more of a secondary idea if the five seven were to be a bad HD gun, the weaponlight is also for muzzle rise, but also fills the purpose of a red dot, which would be difficult to find for a HK, the reason I picked .40 caliber is because the extra stopping power while still actually being a improvement over the USP9s standard capacity because of the mag extension.
Thanks for asking, by the way.