I don't have any of the SDH104K1A's (AC4400), but I do have three of the SDH104K1B combos in a trio of Kato SD38's.
They were inexpensive, easy to install, they run well, and they sound reasonably well.
They're also easy to program (no programming booster required), they fully support CV readback, the sounds can be changed out if you want, and they don't have the inrush issues that so many sound decoders seem to have.
So while they may not be the "best" sound decoders (depends on your definition of "best"), in my opinion they have a lot of positives and are a good value.
Steve