Using Airplay you can stream music to multiple Airport Express units or Apple TVs in different locations at the same time.
I tried a SONOS a while back and found the sound quality streaming lossless ripped CDs with the SONOS internal DAC was not as good as an Airport Express or Apple TV with my external DAC.
I also tried a Node2 and found the sound quality with the internal DAC was better than the SONOS but still not as good as an Airport Express or Apple TV with my external DAC.
When I used the Node2 with my external DAC, I could not detect any difference between it and the Airport Express or Apple TV.
I am not saying the SONOS and Node2 are bad, they work fine for what they are intended, but you can achieve better sound quality with a separate DAC.