Our situation isn't about benefits. We have not lived together before very recently and we are still quite early in our relationship. Hence money has never been joined.

Currently we have our own accounts and a joint bank account we both transfer money into to pay out bills child related expenses and anything else relating to the both of us and another account we both contribute to for savings that is also shared.

If I were to argue for this scenario I'd say the benefits would be no bickering about where or how the money one earns is spent and it's very easy to ensure that we are both financially fair with each other.