PLAYER_LOGIN vs PLAYER_ENTERING_WORLD?

[Krainz]

I'm writing a code that changes the textures and positions of other frames created by other addons, and I'm learning how to handle events better

I've come upon the PLAYER_LOGIN and PLAYER_ENTERING_WORLD events. They seem to mean the same thing, but I'm sure they don't.

What event is the best one to handle when altering UI elements created by other addons? Login or Entering World? And are there any possible drawbacks of choosing one over the other?