I have the Arc, 2 Subs, and had 2 Ones. I upgraded to 2 300s and yes I think it's worth it especially for movies with Dolby Atmos. Worth it.

In short: yes. The Era300 is in a different league. But above all, they have Atmos. If you're happy with the current sound and money is an issue, I'd stick with the One. If you want Atmos and have the installation space and money for the Era, the upgrade is worth it in my eyes.

It looks nice, but in our large and high room it's no good at all...
Above all, we should slowly say goodbye to Sonos. The software is so miserable.
Something always doesn't work. At the moment, you can't select Sonos for the alarm clock setup via Android, only radio.
It's really terrible. They've been promising improvement for years...