If both methods for solving the problem are equally good, regarding the choice between them you could say:
It's as broad as it's long.
Macmillan says this expression is
used for saying that you cannot choose between two things or actions because they are equal
Macmillan also words the phrase slightly differently than I know it: It's as broad as it is long. It also lists the phrase as British and spoken.
The spoken is important. This phrase is definitely conversational and not technical: you wouldn't write it in a paper. Hence, this is really only an answer to your first question: [Are] there any terms/phrases or succinct ways to describe such pairs of methods?
I always took it's as broad as it's long to suggest a piece of wood that could be sat on either side: it wouldn't matter which, as it is square. That may well not be its actual origin, but it does express the equilateral geometry of the metaphor of the phrase.
With it's as broad as it's long, the essence is that it would make absolutely no difference if you went about solving the problem one way or the other, but the choice must between two equivalent options. (You could try it's as broad as it's long as it's high for three interchangeable alternatives, but at that point you've gone off piste and you're on your own.)
(Personally, I think the idea of exact equivalence might be more elegantly expressed by: it's as broad as it's wide. However, I couldn't recommend that as an option!)