Just to expand or say it differently:
(1) If I were building a team in the regular NBA, I would take Moses over Artis because of Moses' mental advantage in terms of aggressiveness / assertiveness / dominating his opponent / making full use of his talent to destroy his opponent vs Artis more passive laissez-fair style of play.
I mean Artis has the skill and physical talent to be a 30ppg scorer in the NBA. He just didn't have the mentality. Moses Malone did. He was a killer out there. If you are building a regular NBA team, you want the killer. It is too hard to have a team loaded enough (in talent) to where Artis can add more than Moses can.
(2) However, in a league of All-Star teams that are loaded with scorers, I reckon Artis has a strong case as the better player vs Moses because of Artis superior ability to influence games in non-scoring ways.