These sit in different price classes - KEF LSX II costs roughly 2.2x what ELAC Debut DCB41 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 |
|---|
| Bass |
B |
KEF LSX II digs deeper - 54Hz against 66Hz. |
| Built-in power |
B |
KEF LSX II has the bigger amplifier (200W vs 100W RMS). |
| Connections |
B |
KEF LSX II adds Wi-Fi and streaming. |
| Size |
depends |
KEF LSX II is easier to place; ELAC Debut DCB41 is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability |
depends |
ELAC Debut DCB41: a sub output; KEF LSX II: a sub output. KEF LSX II sits in a wider range (10 models), so a matched surround system is easier later. |
| Price |
A |
ELAC Debut DCB41 is cheaper - $599 against $1,299, about 54% less; arguably a different class. |
A ELAC Debut DCB41
B KEF LSX II
depends neither is better in the abstract - it turns on your room, placement 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, ELAC Debut DCB41 costs about 54% 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. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 66Hz anyway, which makes the cheaper ELAC Debut DCB41 much easier to justify. Think about the whole system, not just the speakers: the roughly $700 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.