it's six of one and half a dozen of the other
six of one, (and) half a dozen of 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 of one, and half a dozen of the other. John: "Would you rather have pepperoni or sausage on your pizza?" Bob: "Eh, six of one, half a dozen of the other."