"Shottie" kinda irks me. I doubt that Miyashi called his best tools "Katy" for his Katana or "Washi" for his Washikazi. Respect for the hardware, IMO, is a good thing.
But to the real issue here......
The KSG may or may not be a viable HD tool,it's too new to have established a track record.
Like Brent, I opine that the dual wide track mags may adversely affect handling.
The two HD 870s here have mag extensions but handle well. Frankenstein has no extension, but with a short barrel handles FASTER than the HD tools. They're by no means slow, but Frank is Rattler fast. So is the little 20 gauge Express with it's 21" barrel.
Home defense crises rarely require more than a shot or two. It's burglars, not The Battle For Hue. Except for very rare incidents,what's in a standard pump or auto will be more than enough for reducing the threat level to acceptability.
And for those exceptions, we do practice reloading drills, do we not?