The short version information_schema is the SQL-standard way to query metadata portable across databases, slower, limited to what the standard defines. pg_catalog is PostgreSQL-specific faster, more detailed, has everything. Use information_schema for simple queries you might run on MySQL too.
Source: [Dev.to](https://dev.to/not_varunkv/informationschema-vs-pgcatalog-which-should-you-query-4e07)