Siblings in ELAC's Vertex Series III series, so they share a family sound. It comes down to size, output and price.
| Area | Better | Why |
|---|
| Bass | evenly matched | Much the same reach (42Hz vs 42Hz). |
| Amplifier needs | evenly matched | Similar sensitivity (88dB vs 88dB) - both want much the same power. |
| Size | depends | ELAC Vertex Series III IW VJ63 M is easier to place; ELAC Vertex Series III IW VJ63 L is bigger, which usually goes with fuller bass. Your room decides. |
| Price | A | ELAC Vertex Series III IW VJ63 M is cheaper - $6,598 against $9,596, about 31% less. |
A ELAC Vertex Series III IW VJ63 M B ELAC Vertex Series III IW VJ63 L
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 $2,998 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.