When I thought of this question I thought it wasn't very interesting because it seemed a "no-brainer" to me, but then I asked two people and between us we covered all three possibilities, so I guess it's not so clearcut

Imagine you are going to play with your regular partner in a big teams event.
You can have any pair in the world you like to substitute in for you in ONE area of the game:- bidding, declarer play, or defence. The rest of the time they sit out.
So if you choose bidding, they bid the hands then you have to play them (or defend them), etc.
What area would you choose? Feel free to name your preferred pair if you like although that's not so important.