Storm, I've been fortunate to have a lot of experience with subsonic rounds. JD Jones is a very good friend and I have killed game with all his Whispers from 6.5 to .500. The .300 Whisper is the most practical and reasonable cost one to shoot. I've taken 115 deer ,3 turkeys, 1 fox, and 139 groundhogs with it.
Here's a few things I've learned from JD and my experiences. The .300 Whisper was developed around the Sierra 240 gr. HPBT Match bullet. The original subsonic bullets killed by tumbling, not expansion. 220 gr. Match bullets are not quite long enough to tumble reliably. I shot deer with them and they gave no sign of being hit. It took 5 minutes for them to die.
Oddly, Sierra 220 gr. ROUND NOSE bullets do tumble and kill all the game I've shot with excellent results. As far as using the newer Hornady subsonics, I haven't used them, but realize a bullet going less that 1050 fps that only expands may not give good terminal results.
One exception to the light bullets are Lehigh Defense Controlled fracturing bullets. I'm a tester for Lehigh and have taken around 50 deer with their 186 gr. Controlled Fracturing. It has a skived nose with 4 pedals that break off when hitting game. It also has a .17 cal. HP bullet in the nose. With the pedals, the .17 cal., and the solid base of the bullet, you're getting 6 tracts of damage in an animal. This is THE ONLY subsonic bullet I've used that reliably drops deer in their tracts (about 90%). With other subsonic bullets, if the deer is alert when shot, he'll run until it bleeds out(that could be a long way). If not alert, they'll stand around (and some even keep on feeding), and drop in 30 seconds or so.
Deer shot with the .338 & .375 Whisper don't provide enough resistance foe the heavy bullets to tumble much. The .500 Whisper does excellent with 750 gr. Horn. AMaxes. I killed 15 deer with them while testing for a certain government agency. This is a very expensive round to set up. The .300 Whisper (Blackout) is the way to go.
I've had such good luck with the 186 Lehigh and 220 RN that I see no reason to try the Hornady. I have shot a few, but they hit so far from the other 2 that my gun would need to be resighted & I'd be forced to use the one bullet. As it now, with my mil dot scope (needed for subsonic rounds) I can shoot 240, 250 Sierra Match, 220 Sierra RN, and 186 Lehighs without a change of my scope.
I hope my experiences help you some.