No single best speaker here - they are built to different priorities, and the right one depends on your room, your sources and what you listen to.
| Area | Better | Why |
|---|
| Connections | A | KEF LSX II adds Bluetooth, HDMI and digital inputs. |
| Size | depends | KEF LSX II is easier to place; Sonos Five is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | KEF LSX II: a sub output; Sonos Five: a sub output. |
| Price | B | Sonos Five is cheaper - $1,098 against $1,299, about 15% less. |
A KEF LSX II B Sonos Five
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
The usual trade-off: KEF LSX II measures better, Sonos Five costs about about 18% more% less. Whether that gap is worth the money is the call only you can make - and in a normal room it is often smaller than the numbers suggest. In a large or open-plan room, Sonos Five has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, KEF LSX II is the easier speaker to get right.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.