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 | JBL 4329P digs deeper - 28Hz against 37Hz. A subwoofer would even that out. |
| Built-in power | evenly matched | Similar onboard amplification (700W vs 600W RMS). |
| Connections | A | Sonus faber Duetto adds HDMI. |
| Size | depends | Sonus faber Duetto is easier to place; JBL 4329P is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | Sonus faber Duetto: a sub output; JBL 4329P: a sub output. |
| Price | A | Sonus faber Duetto is cheaper - $3,999 against $4,500, about 11% less. |
A Sonus faber Duetto B JBL 4329P
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. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 37Hz anyway, which makes the cheaper Sonus faber Duetto much easier to justify. In a large or open-plan room, JBL 4329P has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, Sonus faber Duetto 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.