You will almost universally get better sound at a better price if you go with a traditional 3.1. For the same cost of of a Sonos Playbar + Sub, you will get a kick ass system with a 3.1 (Front/Center/Left, Sub, Receiver) setup offering much better audio than the Sonos playbar + sub. The good news is that you can easily integrate your 3.1 system into your Sonos ecosystem by purchasing a Sonos Port (https://www.sonos.com/en-us/shop/port.html). Therefore it gives you the best of both worlds. Have amazing sound with the 3.1 and also be able to integrate it with your other Sonos speakers around your house. And if you ever plan to upgrade to a 5.1 full surround / Dolby Atmos set-up in the future, you can easily do so with the 3.1 starting setup.
That's basically the setup that I have in my house and it works very well.
That's basically the setup that I have in my house and it works very well.