What league would you buy into? Remove Fandom and personal preference. Strictly from a financial investment opportunity. Which has the biggest return potential on investment?
P.S. Don't be lame and say "I wouldn't." If you wouldn't, don't post.
I'd lean toward MLS or E leagues. NFL is still king, but I can see health of players turning parents off from peewee leagues thus shrinking Fandom in the future. I think the NBA is getting woke and going broke, and other leagues are dying.