If you search IPI in the forum , there was discussions showing the IPI are not distributed uniquely worldwide and you cannot just think there is only one per artist name, strictly.
So don’t worry too much about them, you can just list them all.
I’ve seen many times cases where different IPIs are assigned to variants of a name like Name Surname vs. N. Surname (which seem non-intentional and just a mess). For cases where the choice of separate IPIs seems intentional, I’d list the info in the annotation for now.
I’ve seen this happen myself. I have even seen ISWC have the same work listed more than once when BMI/ASCAP does not.
There is no one simple answer because there are different reasons why we may get different results.
To answer the first question, I find BMI and ASCAP easier to work with - user friendlier. So that is where I would go. Especially considering that they are the originators of the data.
The second question is, again, one of those different reasons/results kind of questions.
In g…
https://community.metabrainz.org/tag/ipi