Nothing wrong with a shotgun + slugs, especially if you are familiar with the platform. I would stoke my HD with slugs, but I am in the city, so 000 or 00 buck it is.
In my truck shotgun, I loaded with with buck, but had slugs on hand.
Slug-wise, for anti-personnel, I favor foster slugs. For critters, brennekes. Up to 15 yards, buck is king for terminal effects. Past 15 yards, slugs rule. 5.56mm, while effective in it own way, is sucking hind teat until 100 yards when its high velocity, low mass projectile allows for easier hits and rifle-round damage.
One thing the AR guys don't get is the quick handling and pointability of shotguns, even stoked with slugs, and especially vs moving targets. No AR made is as good vs moving targets. A light is nice, but no night sights or red dots needed, thanks. Heck, my primary fowling piece had the bead fall out and I bust clays just as well as when I had the bead.
That said, out in the desert, where ranges are long, an AR15+Leupold 2-7x scope might be my choice. I have plenty of time behind AR15s, too.