Equitable Tax Return Division Between Spouses?

Hello- I'm looking for some help thinking about this issue the right way, and making calculations that are fair for both of us. Here's the deal.

The wife and I are happily married and generally keep our finances separate for a variety of reasons not relevant for this discussion. We're preparing our income taxes and have run the numbers both ways: Married filing jointly and Married filing separately. We've filed each way in previous years depending on our life situations that impacted our tax bills. Through my employer's payroll deductions, I have already had enough withholdings to cover what I owe. The wife did not work outside the home last year, and had approx 66% less earnings than I, as she attempts to get a business off the ground. She also had some taxable stock distributions, on which no taxes have yet been paid.

The figures our CPA ran say we're best off as a couple filing Married Jointly this year, which I'm fine with. But from that return that we'd get back in that scenario, I need to know how between the two of us, we can decide who owes each other how much and which of us is owed what refund amounts for Federal (we've overpaid), State (we owe), Local (we've overpaid), and School taxes (we owe a little).

Do I use our individual tax rates compared with our earnings? do I use what I've paid in, compared to what I owe, and look at the difference? and same for her? I really am confused about how to think about this. Thanks in advance.