My reason to prefer the S3 API is one of convenience/key management really - my
aws CLI is already configured with a B2 profile, so using it would avoid needing to do something new with B2 env vars.
However, if the B2 backend is somehow optimised for B2 - i.e. behaviour or at least implementation is slightly different to be cheaper/faster/whatever - then it’s probably worth the bother.
Thanks in advance,