I think if I'm going to out source auth, I'd rather have a comprehensive solution from a major player, the security here is more important than most other places in software.

Relative JS size comparison doesn't matter directly, it's more about the time to first draw, which has many more factors to add on top of just total asset bytes.

Integration with the new apple login is much more of a priority than passwordless login. Hardware keys would be the next method for passwordless, with many other more compelling reasons to boot.