also: ごじゅっぽひゃっぽ
six of one, half a dozen of the other; much the same; no real difference
Used when two things are essentially the same despite appearing different; often implies that arguing about the difference is pointless. Originates from a Chinese parable where a soldier who retreated fifty steps mocked one who retreated a hundred steps.
Whichever you choose, it's six of one and half a dozen of the other.
Their arguments are much the same; neither can be called correct.