Six of One, a Half Dozen of the Other

What does the idiom “Six of One, a Half Dozen of the Other” mean?

Definition:

The two choices have no significant differences.

For example:

“It doesn’t matter to me whether we go food shopping first or get the car’s oil change—it’s six of one, a half dozen of the other.”

Notes:

Ourside the USA, “a six and two threes” is also used.