It's not a big difference but Marion has played his whole career in a system that was perfect for his skills and now with Nash orchestrating the offense, Marion has it perfect for him.
That system would also be perfect for Odom who has more skills than Marion and I believe Odom would be an absolute monster if he was in Marion's position.
Now true, Marion's less injury prone and more accomplished but from the skill standpoint, I think Odom is much better and would be amazing in the Suns system with Nash feeding him.
Boris Diaw was great for the Suns 2 years ago. He just showed how much you can thrive in that system as a passer.
Odom too is very versatile player and would be just amazing in the Suns system.
Marion OTOH would struggle with the Lakers halfcourt game as he always does.
Both players need to run. Marion is a better hustle guy while Odom is more skilled and talented. I think circumstances are what really counts here.
Marion is in a perfect position while Odom is not. That's what it's about IMO.
The Lakers would not improve with that move, at least Odom has some skills for the triangle although it's far from an ideal system for him.