Advantage of ORDS service call in vbcs and cons of OIC call in vbcs

Hi experts advantage of ORDS api over OIC calls in vbcs .

suppose ORDS being called in OIC for VBCS services what is the disadvantage its better approach or not?

what is the difference between BO (tenancy DB changed to ATP) and ORDS.

Actually client is saying he is not able to provide security url layer over apex url so he suggest go via OIC calls so we need solid reason to deny OIC route for vbcs services data invoke.