A generation apart: JBL Stage 240H is the newer design, against a 2018 model. Newer is not automatically better, but the older one is more likely to be discounted or near run-out.
| Area | Better | Why |
|---|
| Bass | B | JBL Stage 240H digs deeper - 100Hz against 180Hz. |
| Amplifier needs | evenly matched | Similar sensitivity (85dB vs 85dB) - both want much the same power. |
| Size | depends | ELAC Debut 2 0 A4 2 is easier to place; JBL Stage 240H is bigger, which usually goes with fuller bass. Your room decides. |
| Cabinet | depends | Ported vs Sealed. Sealed is tighter and happier near a wall; ported digs lower but wants space behind it. |
| Price | evenly matched | Much the same money ($279 vs $299 a pair). |
A ELAC Debut 2 0 A4 2 B JBL Stage 240H
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?
JBL Stage 240H 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 180Hz anyway, so judge these on the other rows instead. In a large or open-plan room, JBL Stage 240H has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, ELAC Debut 2 0 A4 2 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.