Best answer: A USB-C dongle can be better than USB-C headphones. It all depends on the presence of a Digital Audio Converter (DAC) and its quality. If the DAC in the dongle is better than the DAC in the headphones, then you should go with the dongle. If the opposite is true, then don't bother.
Hi Fidelity components make a difference
The arrival of USB-C brought about an all-new set of audio over USB standards. These are a set of rules that every manufacturer can follow if it wants to make sure its products — in this case, USB-C audio equipment — is compatible with another company's product. The USB-C audio standard is very broad in scope, but one thing it does when it comes to headphones or speakers is allowed a USB-C port to transmit either analog or digital audio depending on what's plugged into the port.
A 3.5mm headphone jack can only transmit analog audio. That means it is completely dependent on the source to provide high-quality sound. If that sound starts off as a digital file — like an mp3 file on your phone — it needs to be converted from a set of ones and zeros to an analog waveform that can be played back through a speaker. Digital audio files are small and writing them to a phone's storage is easy, so they're a great way to store your music or a podcast. But you can't hear a digital file.
High-quality headphones usually have high-quality parts. you can't go wrong with the Razer Hammerheads.
A tiny chip called a DAC (Digitial to Analog Converter) takes the ones and zeros of a digital file and translates them into a soundwave that speakers can play back and our ears can hear. Your phone has a DAC inside it but it might not be used for standard audio file conversion (it's still needed to hear while on a phone call) so many USB-C dongles and headphones have one built in. When they are plugged into your phone the digital file is sent over the USB-C port and gets decoded inline.
A DAC is cheap. The part itself doesn't cost more than a few dollars, but the way it's implemented into a circuit makes a huge difference. The wiring and shielding on the circuit board can make a big difference so inexpensive mass-produced and cheap products — like a USB-C headphone dongle, for instance — can have a wide variance in quality. I've tried more than a handful of USB-C headphone adapters and found one or two I really liked as well as many that were noisy and introduced static into my music.
You can get lucky and buy a USB-C dongle that sounds great. I've had luck with
There are a handful of great USB-C headphones available, and our pick of the bunch would be the Razer Hammerheads. They sound great, are built from aluminum with high-quality drivers (think speakers here), and have a nice tangle-free flat silicon cable. They also don't cost hundreds of dollars.
A dongle could be as good or better sounding than the Razer Hammerheads, but you'll have to try several or get lucky for it to happen. If you want to go for the sure thing, buy the Razers.
Razer Hammerhead USB-C
The sure thing
The Razer Hammerheads are a sure-fire way to get a good DAC and good audio through the USB-C port on your phone. They're also built well and won't break the bank!