Shoot that's about 80% of our bandwidth lol.There is so much overlap in performance that to say one is better than another means cherry picking which traits you want to claim matter the most.
IMHO any line drawn is going to be arbitrary because there's so many other variables.What have you seen that causes you to believe that the 6.5 Grendel and 6.8 SPC II aren’t adequate for deer size game
The 6.5 and 6.8 certainly offer a little more margin for error over a 223 but I'm just not sure exactly what the shot looks like that I wouldn't take with a well constructed heavier 223 bullet that I'd take with 6.5 or 6.8.
In Kat William's voiceas for the 224 Valkyrie it was DOA because federal screwed up the twist rate and ammo at the launch it will never have the following of the first 2 mentioned
"They screwed up ev er re thing"
I went down that rabbit hole only when I stopped chasing the hype that I realized what it did well was put the performance of a long barreled 223 loaded longer than SAAMI OAL sleek 80 grain class VLD bullets and shoot out to 1000 from a mag fed 20" AR.