The JET JJ-6HHDX is JET’s smallest jointer, and identical to the JJ-6CSDX, except for having a helical cutterhead. The spiral cutterhead is its main selling point, and makes it a clear upgrade over the JJ-6CSDX.
The helical cutterhead has 27 carbide four-sided inserts that can be individually removed and replaced. The spiral cutters are quieter and give better jointing results, especially on difficult grains. They are also easier to replace, and last longer due to their four sharp sides.
The JJ-6HHDX is a compact machine with slim, but relatively long cast iron tables. Its 1HP motor is somewhat limited, but given the maximum jointing width of only 6 inches, it should be powerful enough. The small width capacity can be a limited factor when jointing board faces, and may require you to rip boards, joint them, and then glue them back together.
The jointer also has a rabbeting ledge, and front-facing handwheels to raise and lower the cast-iron infeed and outfeed table. Another useful feature is the fact that the fence can turn 45-degrees both ways.