> I have never seen any system (planes or elsewhere) that splits multiple voice communication inputs so you hear different streams in different ears.

PS Engineering PMA450B is one, but most GA aircraft I’ve flown work like this.

> How would that be different

It would be different based on the fact you’d hear one conversation in your left ear, and another in your right ear.

> (let alone better)

Beauty is in the ear of the beholder.

> It's not like your brain can process each ear separately.

Different brains function differently.