is there any advantage of one over the other A-PAC/U-HID/Kadestick i.e. performance-wise?
Haven't done a side-by-side comparison.

Haven't had any issues with KADESTICK and haven't read of any issues with A-PAC or U-HID.
There are differences in price and features.
U-HID is more flexible -- it can do gamepad buttons, keystrokes, mouse buttons, etc.
A-PAC and KADESTICK can do gamepad buttons.
If you've got to have keystrokes, you can either get the U-HID
or hook up two encoders, analog and keyboard.
If you go with two encoders, that adds U-HID Nano as an option.
Scott