One thing I find useful about enums is that they can be used as both types and values, which is ergonomic for decorator-based libraries (like class-validator, nestjs, mikro-orm, etc). The best approach I've found in union land is using const assertions and typeof, which I don't love.

Agree with the author that in almost every other way unions are better though... they play much more nicely with the rest of the type system. I find it endlessly annoying that I have to refer to enum members directly instead of just using literals like you can with union types.