six in one, (and) half a dozen in the other

The difference between these two options is negligible, irrelevant, or unimportant; either option is fine or will work as well as the other. Well, we could take the freeway to your mother's house, or we could cut through the city. It takes about the same amount of time, so it's six in one, and half a dozen in the other. John: "Would you rather have pepperoni or sausage on your pizza?" Bob: "Eh, six in one, half a dozen in the other."