I'm not sure I understand the difference?
The PIC is still the PIC regardless of who actually has their hands and feet on the controls.
We regularly have discussions enroute about the best course of action, sometimes the LHS points out something I don't know or haven't considered and sometimes I highlight something the LHS hasn't noticed or thought of.
At the end of the day, as PIC, they get "final say"... And as long as they can reasonably justify their decision, and it isn't going to kill me, I'm happy to go along...
As far as the "Captain and his co-pilot" method goes... I'm fairly sure there are a number of "Air Crash Investigation" episodes which highlight why things are different these days.