Ok, I have Roland FA-06, Casio PX-5S, Casio LK270, Korg Microstation and EMU Xboard-61.
Overall MZ-X500 beats in terms of easy quick access/fun/possibilities/touch control/sounds/speakers all above.
MZX have the Best (semi?)-weighted keybed, is solid/feel almost as weighted piano keys, it beats PX5S weighted keys, as MZX ones are very fast/responsiver, you can trigger small velocity sound with small pressure, its like fast synth action with weighted piano keys feel without the noise/bad small pressure respons as PX5S hammered keys.
Roland FA-06 keybey is cheap noisier plastic standard, totally unweighted feel organ/synth action, it feels the same as the Xboard.
If I hadn't a lemon MZX, the all-in-one MZX beats above for quick music fun.