The Lakers got the shorter, older, stronger, less effective player. That said, Artest scores a lot more points a game than Ariza.
So I have a lot of thoughts about this trade. In my mind Artest is the better player than Ariza. Thats possibly because Ariza had less points than Artest, and points per game skews value.
Trevor Ariza's PER last season was 15.51, Ron Artests' PER was 15.64. Therefore they were essentially equivalent.
That said, Ariza played only 24.4 minutes per game while Ron Artest played 35.5 minutes a game last season. It might be easier to have a high PER with less minutes played.
Its getting late and I want to go to sleep, so I'll hopefully write more on this topic later.