I really really really like Knex. While Mongo claims to be "easy" and "js-native", It's far easier doing complicated queries with Knex on Postgres than on Mongo with the official client.

I work on a mongo project and doing aggregate queries is really ugly and painful. Everyone praising mongo probably never made "advanced" queries like that or dismissed SQL as shitty and unsecure without ever using it.

I personally wouldn't consider Knex an ORM. I'd describe it more as:

A cohesive set of functions that help you build and execute SQL operations.

Likely also better performance with just using Knex. Any ORM likely adds overhead, Sequelize definitely does, although we keep working on reducing that overhead - But inevitably features === overhead.