Rapunzel definitely seems more childlike but that makes sense story wise as she had spent her existence locked in a tower with only one other person and a lizard. Anna, at least, interacted with her parents and the other palace staff and received an education so while sheltered she isn't ignorant of other people and the outside world.
That aside, I thought Tangled had the more complex villain and by a long shot. Mother Gothel's relationship with Rapunzel is probably the most complicated villain/princess dynamic in any of the films. Hans, on the other hand, was vital to the plot twist but otherwise pretty one note and his plan was kind of odd once you think about the way royal succession tends to work. Killing Anna and Elsa just paves the way for their fourth cousin or similar relation to take over.