Overlay VS Hacking

[AZBZ 0]

I'm thinking of overlaying my toilet floor and wall tiles. 

Was hoping you can share your experiences with overlay. I know overlaying is cheaper but theres a risk of popping tiles. So I just want to know if any of you experienced it before. 

[Robin Hoot 0]

Honestly, overlay or newly laid, want to pop will pop. Do a tap test before overlaying?