Flyway and liquibase together?
I've looked at both Liquibase and Flyway individually and on an individual comparison alone, Liquibase seems like the better tool for our needs. Some sources mention using both Liquibase and Flyway together. Liquibase seems to have everything Flyway has and more flexibility when it comes to rollbacks. The main advantage of just Flyway seems to be not having to use XML, but Liquibase allows you to specify an SQL file in their XML.
Basically, I'm still not clear on what the benefits of using Flyway & Liquibase together would be over just Liquibase, if there are any. Maybe there's a way to do it I'm not seeing as even if Liquibase was referring to valid Flyway SQL files, both tools would have to be run independently and still have the same pitfalls even though you could technically use either tool.
Answer
A small correction, before I answer question. The assumption
Liquibase seems to have everything Flyway has
isn't correct. Flyway shines when it comes to parsing SQL. You can use unmodified SQL files generated by your native tools containing all kinds of complexity like PL/SQL packages and procedures, MySQL delimiter changes, T-SQL, PostgreSQL procedures, ... With Liquibase you would have to split these in individual statements, add extra comments to the SQL files, ...
The beauty of being able to use your SQL files as-is is that you avoid lock-in. You can take your existing SQL files, start using Flyway with minimal investment and moved away later if it doesn't suit your needs anymore. Not so with Liquibase.
Also the issue of down migrations (think of them as compensating transactions, not rollbacks) is really something that sounds great in theory, but that is almost never needed in practice. See https://flywaydb.org/documentation/faq#downgrade
However when it comes down to using one or both, I certainly agree with SteveDonie (Liquibase team member) that using just one instead of the both together is almost always the better choice.
Disclaimer: I am Flyway's creator