I would say NFL players are stronger. Athleticism varies player to player, and both games require different skills.
NBA games have less and shorter breaks than football, so NBA players have to exert more energy per game.
I’d still give a slight edge win to NFL players even with my biases towards American football. It’s kind of a dumb game. It’s like turn-based rugby. And make competitive catch less dangerous.
Poor defense. Doesn’t matter who it is. It’s the NBA