Is it better for two couples at a restaurant to split the check at the end or ask for seperate...

Separate checks are very helpful, so maybe ask for those unless someone in the group feels more comftorable getting the one check and having everyone work it out themselves. If you don’t run into this problem separate checks are easier to pay when the people going out to eat have different methods of pay from each other or if anyone is paying in cash to avoid confusion with extra change and tip money.