I think P1 and P2 teams would ultimately take the spot, but in the newer age of the series I vote Persona 3 SEES as the most powerful. Compared to p4 and p5. SEES had actual skills across the board, where each member could take out their respective counterparts in p4 and p5. I do admit Naoto Shirogane is an exceptional team member from the p4 cast.
P3 MC is also superior to Yu and Joker in all regards, with and without the ultimate arcanum. He is a master in all weapons (except firearms). I do admit that Joker is likely a lot more agile though. Yu just doesn't compare to either though.