It's a huge difference in usability if you need to plug it into a TV, and turn on the TV to listen to music.
But this is all water under the bridge because there won't be another Chromecast Audio. The product was cancelled due to low sales (no thanks to Google's lack of marketing and promotion) and meanwhile the industry has gone in the direction of smart and connected speakers.
Which is a shame because the Chromecast enabled the democratization of access to media systems for small players who could leverage a pretty straightforward set of APIs on mobile and/or web apps to broadcast their media to pretty much anything using the Chromecast onramp, and at low cost for the consumer.
Now if you're Spotify, Apple, Amazon, Tidal, etc., you don't give a damn about the demise of Chromecast tech -- other than being silently happy that a whole set of smaller competitors are impacted -- since smart/connected speaker manufacturers are more than happy to limit their products' capabilities to a small and exclusive set of solutions like Spotify Connect, Tidal Connect, etc. While many still support Chromecast, they will no longer have to when all the small players are forced out of business.
Qobuz should be able to hang on for a while through their Roon relationship, but IMHO Roon's continued viability is uncertain, particularly when Apple, Amazon, and Spotify are all providing CD quality or better with their streaming services, and when Amazon and Apple finish building out Roon-like experiences with an amalgamation of local and streaming music through integrated hardware, software, and cloud technology. Spotify may have to use partnerships to do the same, but they should have plenty of motivated and well-heeled suitors.