An idiom meaning that there is very little difference among items or people — much of a muchness; all pretty much the same.
彼らの成績はどんぐりの背比べで、順位を決めるのが難しい。
Their grades are so similar it's hard to rank them — they're much of a muchness.
どのメーカーの製品も性能はどんぐりの背比べだ。
The products from each manufacturer are pretty much the same in performance.
小さな会社同士の競争は結局どんぐりの背比べになってしまった。
Competition among the small companies ended up being pointless — none stood out.
An idiom for pointless competition between two or more equally unimpressive parties — a petty contest (a 'pissing contest').
売上で争っているが、実力はどんぐりの背比べだ。無駄な争いだ。
They're fighting over sales, but their abilities are about the same — it's a pointless fight.
二人の議員の言い争いはどんぐりの背比べに過ぎないと有権者は言った。
Voters said the quarrel between the two politicians was just a petty contest between equals.