I think it is only higher quality audio.

Seems like they are suggesting the AI they use to dynamically configure your sound based on room placement is only available in this model.

So I was a Sonos owner and I loved them, when I sold them to buy Google Home's I was greatly saddened by decrease in audio quality. It looks like this is the Sonos replacement? Seems weird that they wouldn't just re-brand this as Google Home+ or something similar.

I am getting a very similar vibe similar to Apple iPad's where you can buy an iPad at pretty much every dimension you want. Same now with Google Home, you can get a small, medium and large Google Home... but with confusing branding.