The in-laws are a boundary problem, not a loyalty contest

Almost every in-law argument is really the same argument, and it is not about the in-laws. It is about whether the two of you are a unit that decides things, or two people who each report back to their own family.

That framing helps because it changes what you are negotiating. You are not deciding whose mother is more difficult. You are deciding what the two of you tell people, when, and who does the telling.

One rule carries most of the weight. Each of you handles your own family. The message that a visit is not happening this weekend comes from their own child, not from the person who married in. Nothing raises the temperature faster than a son sending his wife to deliver a decision to his mother.

And the other half of it, which people like less: your parents do not get an account of your marriage. Repeating an argument to your mother recruits somebody who will remember it long after you have both forgotten it, and who has no way to see the other side.