Pierce Vs Chain on Ice Shot

So, I recently got into a debate with an acquaintance over Pierce Vs Chain. Mostly being over whether or not the harbinger quiver (The Fracturing Spinner or The Shattered Divinity) was objectively worse than Hyrri's Demise. His main point was due to the assumption that "Pierce gets rid of 80% of your damage".

He cited that because of the interaction with King of the Hill's Knockback, an enemy would be knocked back into the cone that was created when they were hit, and then also take damage from it. At least going off of what I can find on the wiki, an enemy can't be damage by their own cone. So unless they can be,pushed back into their cone to take damage from it, I don't understand why he thought so. On top of that, unless I'm mistaken, a crit on a pierce will also push an enemy back, so would the interaction not be the exact same as Chain?

TO clear some things up, the question is not "which one has better clear speed". I know that chain will always beat pierce in that battle. Since auto-aiming towards enemies and offscreening is free with chain, but whether or not that interaction with knocking a monster back would not be the exact same either way