My mom and sister both use "six to one, half a dozen to another". I use the actual form of the idiom, "six of one, half a dozen of the other" and my mom used to correct me. I guess I know why she said it wrong: imagine two people. And one says "It's six", and another says "no, it's half a dozen". They're both the same, they mean the same, but it's six to one (person), half a dozen to another (person).

That said, if I were going to start a Borg-themed band, Six of One would be a kick-ass name.

I like when people use a really abbreviated "six one half dozen another" because it's basically incomprehensible if you don't know the actual phrase.

I typically just refer to it as “six hundred twenty one”

Like Seven oh Nine?