People hunt with pistols, revolvers, bows, and air guns. 300bo is no worse than any of those. A pistol caliber weight bullet traveling at pistol velocities is going to do pistol bullet stuff. There are 30 cal bullets specially made to expand at subsonic velocities. I’m personally of the opinion that if you’re outside of bow range, you aren’t really hunting anyway. Expanding subs and a can are great at close range.
As for supers, E= (mv^2)/2 which may favor the 5.56, but real world effectiveness defies easy calculation.
As for “subsonic fun,” I’ve got better things to do with my limited funds than to make quiet noises at the range.