There is no nutritional difference between feeding mice or feeding rats. Since we don't know the nutritional requirements of Ball Pythons, it's a moot point to say that one is better than the other. Balls do equally well on either.

I like the fact that if I have an adult mouse that doesn't get eaten one week, I can keep it(and it's 150 other mouse friends) for another week and it won't die or get too big. If you buy a live rat pup, which won't be weaned, won't even be eating solid food or drinking from a water bottle, or even have its eyes open, you'll have to euthanize it or take it back to the store if your snake doesn't want to eat it. If your snake eats f/t, great. If it doesn't, then you're stuck throwing money away as well as wasting that rat's life.

Just my view on these things Why fix what ain't broke.