Is the open top or moving cycle the bigger issue?

For a cat that already avoids covered litter boxes an open top sounds less intimmidating because the room stays visible. But an automatic box adds a different thing to get used to which is movement and sound after the cat leaves. That makes me think the shape alone probably doesnt predict whether a cautious cat will accept it or not .A slower introduction new box powered off, familiar box still available, movement added later seems less abrupt than changing everything at once. With cautious cats which part usually matters more? the enclosed feeling or the box moving?