Tough call without knowing where you're at in the game and what your current roster looks like.AA is obviously an incredible champ, but not viable in some content, as he has no immunities. Obviously if the opponent is bleed or poison immune, that's gonna really limit him as well.
Something that no one else has brought up is general enjoyment and how fun they are to play. Archangel may be a great hero but he’s about as exciting to play with as a flat basketball. Apocalypse may not be perfect but he’s still pretty good and is pretty fun to play!
AA can do everything at r4. Apocalypse not only is a great champ on his own,but the horsemen ability is just way too insane.