I cant comment on Motion not having used it, but I've done a lot of cut out animation can say that outside from going full 3D, node based compositors are king for cut out animation (I haven't done any in fusion to date, only Toxik and Nuke but the concepts are the same) the advantages you have in instancing nodes, replacing source footage without worrying about stuffing things up because of different frame size/proportions & arbitrarily adding transforms/axis are just massive when doing cut out work.
the first time you set up an offset highlight/shadow with 3 nodes, then instance that across all your characters creating a global lighting setup you will be all like 'oooooh yeeeahhh'