How does it compress sound?
Using my iPhone 8+ I’ve just tried both my sets of EarPods, the ones that came with my iPhone 8+ and my other set that came with my iPhone 6s+ using the dongle and they sound exactly the same.
Have a couple sets of B&O headphones. Using the Dongle on my 7+ you can (I can) tell the difference.
Still, I did get a higher end BT set.
Now the 8 or X may be different but I doubt it.