The main, and biggest, difference between the ‘Play:1’ and ‘One’ is Alexa – the Sonos One has Amazon Alexa voice assistant built in. Both the Sonos Play:1 and Sonos One have 2 drivers, built-in WiFi, a standard wall plug, and are wall-mount compatible. One difference is the visual appearance of the physical controls on the top of the speaker. The Play:1 has one push button for play/pause/skip, and a rocker button to control volume up/down. Check out our side-by-side comparison below. Comment if you have any questions!
Side-by-side Comparison
Sonos One
Released: 10/2017
Price: $195-200
Voice Control: Yes, Alexa built-in
Drivers: 2
Line-in: No
Wall-mountable: Yes
Physical buttons: touch-capacitive volume and track control

Which came first? The Sonos Play:1
The Sonos Play:1 was the first consumer smart-speaker released by Sonos in October, 2013. The Play:1 marked the genesis of the 1st generation Sonos line, later introducing the Sonos Play:5 and the Sonos Sub.
The Play:1 is WiFi connected and can be controlled with the Sonos mobile app on iOS or Android. The legacy CR2000 dedicated-controller works with this speaker.
Can you control the Play:1 with voice commands?
Out of the box, no. But it is possible.
In order to have voice-control capabilities, the Sonos Play:1 must be paired with a stand-alone Alexa device (like an Amazon Echo Dot). Once paired, your voice has complete control over what is played, when, how loud, and for how long.
The Sonos One does come with Alexa built-in. This is the only major difference between the new and old single speaker from Sonos.
Meet the Sonos One
Four years after the original Sonos debuted, in October 2017, Sonos released the most recently update Sonos One smart speaker, with built-in Amazon Alexa microphone and brain.
This is the only major difference between the new and old speaker from Sonos.
The new Sonos One has a touch-capacitive surface on the top, with printed markings to indicate the touchable hot spots. With the Sonos One touch-control, you can play/pause, skip left, skip right, and slide volume up and down.
The Bottom Line
Both the Sonos One and the older Sonos Play:1 represent high-quality home audio, with the most robust internet-connectivity options found in the newer Sonos One. If you’re looking to add more speakers, and already have Alexa devices, the Sonos Play:1 is perfectly suitable and $50 less expensive.
Driven by consumer confusion arising from the product naming and similarity to the Sonos Play:1, the products are marketed as “The all-new Sonos One Smart Speaker” (new) and “The original Sonos Play:1” (old).
Since 2017, Sonos has been update each of their consumer speakers to include Alexa, enabling smart-home owners to eliminate needing a stand-alone Echo Dot for voice control functionality.
You are a very bright individual!