I don't know I've always thought samus was pretty hard to main, but then again I haven't really mained anyone outside of her so I can't say that objectively. :/
You do have to be really good with her before it starts to come out competitively though, and she does rely on a lot of small ats imo, especially with her ledge game, and you have to learn how to space really well, and put together short burst combos that depend on what situation your in. so imo she is pretty hard. i've heard people say that they've had trouble trying to pick her up, especially getting used to her floatiness, timing, and the situations of her moves. However, i've heard a few others say they thought she was pretty easy too, so idk.
whatever she is, she's pretty **** kwl ^^