Dental caps. Disadvantages of those two?

Zirconia caps are indeed the best because they are metal free, lightweight, more tissue compatible, much high in strength, and translucent just like natural teeth (a metal ceramic or a metal Crown will reflect the light and not refract it because of zero translucency). So if you want the best the answer is simple. But if you have to make a compromise between the best quality and budget you can choose from the other variants also. There are no disadvantages of the other two variants. It is a simple concept that the next generation of crown is better than the previous ones but that does not make the previous ones inferior. Zirconia has multiple advantages but that does not mean that metal ceramic crowns have disadvantages (except for translucency, which is obviously not possible because of a metal Core). Regards.