>>149374120Flamengo is the mass-following, bandwagon moneyball side. Best if you want to fit into a large group and have fun. Fluminense is the side with a minoritarian following and a tradition of producing great home-grown players. Better if you want closer ties to a smaller group with a strong identity.
It's also inevitable bringing up the stereotype of Fluminense fans being socially better off than Flamengo fans.