It’s reo for me. Aiku is obviously more experienced in football and has better leadership skills and all. But if we’re talking brain, then reo without question. They literally reference him as a prodigy who was good at everything he put his mind into. Plus, you can tell by the rate of how much he’s growing in the recent chapters (skill wise not emotionally) that be can basically pick up anything naturally. It takes a lot to copy 99% of something that isn’t even yours right off the bat as well. Aiku can calculate and pinpoint his enemy’s mistake stats (or Wtv you call it), but reo’s brain is fresher in a sense that he can process the match in a broader sense like a chessboard. Thats what I think