Quiz Bowl was full of a ton of smart kids with various interests. We "practiced," but the only skill you could really develop was being able to predict a question before it was finished so you could be the first to answer. Questions varied widely from competition to competition. One time we got to be on local TV to compete, but there really wasn't a season or tournaments. It was mostly 1 on 1 matches after school. Overall it was a ton of fun.
Academic Super Bowl was also full of smart kids, but they were more goal oriented. It was something you had to study for. Before the competition you were given some categories, you assigned categories to teammates, studied, and then competed at various events. It was literally just more memorization. I got drafted to do it one year the night before a competition, because I was The Guy for a topic they needed a teammate for. It was awful. I fumbled my way through because I didn't have near the detailed knowledge required for the specific subcategory. I probably would have done better if I had more time to prep. It was a big tournaments, and at the end there were different prizes for schools by various sizes.
The type of kids in the two were varied. Everyone wanted to get into a good college. The former seemed to love knowledge for the sake of knowledge. While the later had a ton more grit, they lacked passion in areas outside of directed study. The former would read a book, because it was mentioned offhand in another piece of media. The later would read a book because it was assigned to them.
Reading through this thread, it seems like people's experiences of Math Competitions varies from one to the other. Having grit to study and work at it gets you far, but having passion probably gets you further. The issue is grit tends to be fungible while passion is not.