1. Your shooting style.
2. How technically competent you are.
2. The couples preference.
1 because your style might be more artistic and colours might look odd or b/w just looks 'better' to you.
2 if you consistently under/overexpose then you will have to edit 100% of your shots right? Some people shoot jpg and apply tone curves within the camera and make it a 1 shot one kill kinda thing so they dont have to spend so much time in post work later.
3. Everyone has their own preference but assuming they chose you for your style then its purely dependant on #1