I enjoyed Untrainable Dragon more. I would say it tugs at the heartstring a little more if you enjoy the HtTYD series. Cirque Arcanus is pretty neat, but it's based on Fantastic Beasts which has less of the original Harry Potter feel. But it you were a big fan of Fantastic Beasts, then I would go with Cirque Arcanus. I think Dragons is a tiny bit shorter and have more showings, so that can also affect which you can squeeze in.