Iroh showed exceptional agility throughout the series, and all before he got in much better shape in the prison(which he broke out of single handed without firebending) before the finale. I don't think Ozai has more agility or power, considering Iroh blasting the hole in Bai Sing Se was more powerful than anything Ozai performed on his fight with Aang. I also interpreted what Iroh said differently than how some others took it. I took it to mean that he may not have been willing to kill his brother in a fight and would probably be too hesitant if he ever did fight him.
I'm going with Iroh and Zuko for the win, due to Azula being crazy. If she wasn't I'd probably give it to her and Ozai.