is one of them more complete and/or better maintained?

I'm obviously biased since I'm the creator of one, but I do believe mine (factorio-types) is better / more complete.

As far as maintained, I have actions that check for new versions of the Factorio API nightly, auto-build if a newer one exists, and push an updated package to the NPM repo once I approve the workflow.

@GlassBricks

I'm also biased since I'm the creator of the other, but I argue that mine is still much better. Many of the type features listed on the readme aren't present in factorio-types, typed-factorio includes a few lualib modules, includes the settings stage, and allows multiple stages to exist together.

I am interested in how you got the nightly version check to work, though. I'll likely implement that as well.

I see no issue in having both listed, especially because both are maintained.
I think the it's fine if we let the reader/user decide what to pick.