I think Koontz is far superior to King in pretty much every way. The gorier Scooby Doo analogy is funny, because he knows how to be silly when it is called for, but he's a really excellent writer. He knows how to get to the point, unlike King. He writes excellent evil characters, and he knows how to humanize without making excuses for their shitty behavior. (oh they had a hard childhood!!) They're evil and usually irredeemable.
That and he writes awesome protagonists. Really likable, relatable guys that sometimes manage to be angelic in a way. They're flawed individuals, but they work hard and they want to do what's right. And for his side characters, they're not all secretly weird or perverted or have ulterior, creepy motives. They are just regular, relatable individuals who are what they are. He's not trying to be edgy and gross like King. That being said, he knows how to write a despicable, disgusting antagonists, but they pretty much always get what's coming to them in the end and it's extremely satisfying to read them getting their comeuppance. He's not like these authors where everything has to be negative or end on a down note. His books often end on a sad note, but there is still a happy ending in there.