Backdrivability and Variable Stiffness Joint

Hello folks,

Lets assume that a manipulator is backdrivable (*due to cable driven or something like that).

If the manipulator also has a variable stiffness joint by adding a spring adjustment system (at the end of the cable or so), could it be better than just being backdrivable ?

If then, what aspect could be better?

Backrivable joint vs. Backdrivable + Variable stiffness joint

Thank you.