I have both MX500 and RY4S Plus. I think the NiceHCK are really good, not only for the price, but in my opinion the Plus are better in every way. The MX500, in comparison, sound hollow, and with a certain veil. The Plus, instead, sound more open, with more detailed bass (not only quality, but also quantity) and crispier. The real upgrade to the Plus came at home with the M2s Pro, to the point that I have ordered the 150 Ohm gold driver.
Don't take me wrong, the MX500 is really good, and what I call better could simply be a different sound profile for others, but I think the Plus are something special and great, that deserves everyone giving it a try. Even considering the Smabat is superior, I won't miss the chance to buy the 300 Ohm version, that in words of an appreciated member of a spanish forum, is more refined than the Plus.