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 | Triangle Borea BR02 BT digs deeper - 47Hz against 50Hz. A subwoofer would even that out. |
| Built-in power | evenly matched | Similar onboard amplification (100W vs 120W RMS). |
| Connections | A | ELAC Debut ConneX Adsum adds HDMI. |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Expandability | depends | ELAC Debut ConneX Adsum: a sub output; Triangle Borea BR02 BT: a sub output. |
| Price | B | Triangle Borea BR02 BT is cheaper - $499 against $749, about 33% less. |
A ELAC Debut ConneX Adsum B Triangle Borea BR02 BT
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?
Neither runs away with it - they trade advantages. Let the "depends" rows and your own room settle it. Think about the whole system, not just the speakers: the roughly $250 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.