Share the power and the decision-making. Avoid the resentment that comes when one is burdened with responsibility and the other resents being told what to do.
When it comes to decision-making, two heads really are better than one, even if one of you knows far more than the other about a particular subject.
Taking the time to thoroughly explain your rationale for your decision to your partner will clarify all of the information for both of you.
Your assignment, should you choose to accept it:
List the decisions each of you makes without input from the other. Decide which of the decisions are minor and which ones are extremely important to both of you. Review one of the important decisions together.