Some say it maneuvers better... I have to say I notice no difference.
The only reason I fly it is for nostalgic reasons. I think it was able to fight the most when the Allies were just pushing into their great offensive on the Axis in all theaters. The P-38L didn't arrive pretty much until the Allies already had complete utter superiority.
In addition, our P-38L doesn't run at full rated, fresh-out-the-factory power.