In theory, the Y3X switch is not an upgrade to the Y3 switch. Y3X and Y3 cover different sound and typing spectra. Compared to the classic Y3 switch, Y3X is slightly louder and poppier. Thanks to the spherical stem tip and spherical bottom housing contact point (Same as Keygeek Butterfly Switch), Y3X has a mellower and softer bottom-out feel than Y3.
In general, if you are looking for a switch that is creamy and thocky, Y3 would be the go-to option. If you want your keyboard to sound thocky and poppy at the same time, this is what Y3X was designed for.