Both great speakers. The Play 5 has a bit more clarity, bass and is louder. Also, the Play 5 is the only one with the "Line In" feature that allows you to plug another sound source into it like a stereo receiver/cd player/turntable/cell phone/computer. For instance, I have my old school stereo from the 80s plugged into one of my Play 5s and now I can listen to vinyl records all over my house. The Play 5 is the "control unit" for all other Sonos speakers on your system. Not ALL audio sources from the internet are compatible with the Sonos system like "Audible" from Amazon. I listen to books on Audible and I have to plug my cell phone into one of my Play 5 speakers in order to hear my audio books on the Sonos system. Every Sonos speaker will work by itself but you have more flexibility if you have at least one play 5 for that "Line In" feature. It's an investment but worth every penny!