Let's just get to it.
The Mighty Ducks is a sports movie, through and through, because it does exactly what the genre has been built from: it takes a sport and applies what it teaches you to everyday life for the characters so that we get to learn something.
The Sandlot is a good movie, but it takes baseball and says, "Baseball is f-ing life, man!" and then focuses on a farcical romp to get a ball back. Different thing. The sport in question takes a backseat to the plot. Which is fine, but it makes it less of a sports movie.
And can we address something here that even Chris seemed to fall into? The Sandlot abandons the protagonist (Scott Smalls) midway and shifts the focus onto Benny. Why? Because Smalls finished his character arc too soon. He made friends and gained acceptance with twenty minutes left in the movie. And Benny really didn't have an inner conflict or need that was served by pickling the beast. He was respected by every kid in town and had nothing to prove. So what was his dream about? Nothing, really. Other than wanting to be famous.
Meanwhile, The Mighty Ducks is clearly centered on Gordon Bombay, who learns discipline and fair play and self-respect by being forced to teach it to kids through hockey. He even got to explore his father issues, which were reflected in one of his players, Charlie. The sport was teaching the characters (and the audience) life lessons.
And before I go, let's talk about fat kids. Both teams in question had a fat kid who makes wisecracks and talks with a world-weary sarcasm. But between Greg Goldberg and Hamilton Porter, who would you want on your team?
Ham is a dick ... to everyone. Even his teammates. Meanwhile Goldberg becomes a spokesperson for the team at times and learns something about conquering his fears.
There's just more from the Ducks in terms of sports-related fun and lessons. Oh, and less amusement park vomit.