That’s a question asked on Quora and deleted before I posted my answer. So I’m posting my answer here.
This is like asking if a car radio sounds better than a TV. Because it’s a matter of where, how, when, and what, more than a matter of sound.
There is some overlap in the sense that both SiriusXM and YouTube are fully useful on mobile apps. But you don’t watch your radio in your car or listen to your radio on your TV, even though it’s possible to do both through apps that are native to both the road (through Android Auto and Apple Carplay) and the living room (through Roku, Amazon, Apple, and other TV app platforms).
As for the sound itself, YouTiube lets you select audio quality bitrates up to 256kbps AAC & OPUS. SiriusXM’s default bitrate is also 256kpbs, but over the satellite link bitrates are typically lower—sometimes much lower. But, since SiriusXM does not (to my knowledge, so far) publish their bitrates in a place that’s easy to find, its bitrates are subject to debate. Here is one of those on Reddit.
But, again, it’s a matter of where. when, and what, more than how. If you want to see and hear a piece of music, YouTube provides enormous optionality, with its almost boundless collection of videos. If you want radio-like music programming, SiriusXM offers more—plus sports, talk, news, sports (including play-by-play for all the major ones), and more.
Yet the Internet has more than both put together. That’s why the image above is of Radio Paradise, which is one of the oldest and best Internet music stations. It’s live on the Net and the Web, and it has Best Of collections on YouTube as well.
Bonus link (and a lot of fun): radio.garden. There’s an app for that too.