であれ〜であれ

1. 1Pairs two contrasting alternatives to say that the outcome or judgment holds either way.Ex. 1
2. 2Lists representative examples of a group to mean that anyone or anything in that group falls under the same statement.Ex. 2

This is a stiff, written-style expression used in essays, formal speech, rules and opinion pieces. The main clause states a judgment, rule or fact that holds regardless of the listed items, which are usually opposites or members of one category. にしろ〜にしろ and にせよ〜にせよ express a similar idea in a slightly less formal tone, and にしても〜にしても is more conversational.

• 1.
  であれ / であろうとN1「であれ / であろうと」 takes only one item (a noun or な-adjective stem) or an interrogative such as 「誰」「何」「どんな＋noun」 to cover all cases, and it often pairs with 「たとえ」, whereas this pattern must list two items. Both are formal/written and cannot be directly substituted for each other.
• 2.
  にしろ / にせよN2Besides the listing 「AにしろBにしろ」, 「にしろ／にせよ」 can also stand alone to mean “even if... still”; it attaches directly to verbs and い-adjectives, with a slightly softer tone than 「であれ」. When listing nouns or な-adjectives, the two are interchangeable.
• 3.
  といえどもN1「といえども」 works on a single item, emphasizing “even A is no exception”, and it can attach to verbs, adjectives, and minimal quantities such as 「一円」. 「であれ〜であれ」 instead pairs two items to mean either one is the same, attaching only to nouns and な-adjectives, so the two are not interchangeable.
• 4.
  ともN2「とも」 attaches to the volitional form of verbs, 「かろう」, 「であろう」, and the like, meaning “even if... still”; it often pairs with 「たとえ」 or an interrogative and is not used in paired listings, whereas 「であれ〜であれ」 pairs two nouns or な-adjectives. Both are formal/written.
• 5.
  にしてもN2「にしても」 can also be used alone to express concession; when it pairs items as 「AにしてもBにしても」, it is close to 「であれ〜であれ」 and the two are mostly interchangeable. 「にしても」 is neutral in register and can also attach to verbs and い-adjectives, whereas 「であれ」 is formal/written.
• 6.
  なり〜なりN1「なり〜なり」 means choosing one of the listed options and doing it, with the sentence often ending in a suggestion such as 「しなさい」; it attaches to verbs and nouns, sounds more casual, and does not mean “either way is the same”. The two cannot be interchanged.

「であれ／であろうと」 is usually a single-item pattern, often used with interrogatives to mean “no matter what”; 「にしろ・にせよ」 and 「にしても」 are close in meaning but slightly softer in tone and attach to a wider range of forms. 「といえども」 and 「とも」 are single-item concessives stressing “even if... still”, while 「なり〜なり」 means choosing one of the listed options to act on, not “either way is the same”.