These sit in different price classes - KEF LS50 Wireless II costs roughly 2.7x what Sonos Five does. Expect it to lead on paper; the question is whether the gap is audible enough in your room to be worth it.
| Area | Better | Why |
|---|
| Connections | A | KEF LS50 Wireless II adds Bluetooth, HDMI and digital inputs. |
| Size | depends | Sonos Five is easier to place; KEF LS50 Wireless II is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | KEF LS50 Wireless II: a sub output; Sonos Five: a sub output. |
| Price | B | Sonos Five is cheaper - $1,098 against $2,999, about 63% less; arguably a different class. |
A KEF LS50 Wireless 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?
KEF LS50 Wireless II is ahead, but only on 1 of the measured areas, and it costs about 2.7x the price. That is a lot of money for a narrow margin on paper - Sonos Five looks like the sensible buy unless something else about the KEF LS50 Wireless II appeals to you. Think about the whole system, not just the speakers: the roughly $1,901 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
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.