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 |
|---|
| Bass | B | Q Acoustics M20 HD digs deeper - 55Hz against 66Hz. |
| Built-in power | B | Q Acoustics M20 HD has the bigger amplifier (128W vs 100W RMS). |
| Connections | depends | ELAC Debut DCB41 adds HDMI; Q Acoustics M20 HD adds streaming. |
| Size | depends | ELAC Debut DCB41 is easier to place; Q Acoustics M20 HD is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | ELAC Debut DCB41: a sub output; Q Acoustics M20 HD: a sub output. |
| Price | evenly matched | Much the same money ($599 vs $599 a pair). |
A ELAC Debut DCB41 B Q Acoustics M20 HD
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?
Q Acoustics M20 HD has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 66Hz anyway, so judge these on the other rows instead. In a large or open-plan room, Q Acoustics M20 HD has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, ELAC Debut DCB41 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.