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 | evenly matched | Much the same reach (50Hz vs 50Hz). |
| Built-in power | A | Kanto TUK has the bigger amplifier (130W vs 100W RMS). |
| Connections | A | Kanto TUK adds phono. |
| Size | depends | Kanto TUK is easier to place; Audioengine HD6 is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | Kanto TUK: a sub output; Audioengine HD6: a sub output. |
| Price | B | Audioengine HD6 is cheaper - $699 against $900, about 22% less. |
A Kanto TUK B Audioengine HD6
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?
The usual trade-off: Kanto TUK measures better, Audioengine HD6 costs about about 29% more% less. Whether that gap is worth the money is the call only you can make - and in a normal room it is often smaller than the numbers suggest.
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.