Supersonic 300blk is just 7.62x39 for the AR, but worse.
>but it was actually made for subsonic loads out of a short barrel!!
Even if we're comparing apples to apples, subsonic 300blk is literally worse than 9mm:
https://www.youtube.com/watch?v=BnedpQ4xTIo
But 9mm isn't limited in platform like 300blk. There are a shitload of different 9mm firearms in a shitload of different packages for different needs.
>but it was actually made for longer distances!! You can change from subs to supers if you need to!!
So you can do 2 things shittily. Amazing.

It's a poor attempt to make the AR do everything. It's not even good for hunting.