much of a muchness; all alike; no significant difference
Idiomatic expression comparing people or things that are equally mediocre or unremarkable; literally 'height comparison among acorns'.
The grades in this class are all much of a muchness.
候補者の政策はどんぐりの背比べで、どれを選んでも大差ない。
The candidates' policies are all more or less the same; it doesn't make much difference which one you choose.
pointless competition; pissing contest
Used when two equally unimpressive parties compete, implying the competition itself is meaningless.
あの二人の言い争いは、どんぐりの背比べだよ。
That argument between those two is just a pissing contest.