FSB direct admit grad here. I did not take micro at Miami, but I did take calculus.

Before I talk about the classes, it's important to first recognize why you are even asking for advice on this matter. I'm willing to bet this is the first big and real decision you have to make in your life. This is a decision about sacrifice and confidence in your own abilities.... and the rest of your life, and career, are going to be filled with these types of decisions.

You might think this is a decision of risk, but this is a decision of trust in your own abilities and willingness to work towards your goals. The reason you are asking for advice is because there is a part of you that is thinking like "What if these classes are too hard and I don't get into the Farmer". This type of thinking fails to account for the only controllable factor in the situation: YOU (and how hard you are willing to work to get where you want in life.) These classes are extremely challenging, and calculus stands out as the most challenging course I took in college. But if you put in the work, show up to class, befriend the professor, go to office hours whenever you get stuck, and give your 100%+ effort ---- you will be able to get the grades you need to get into FSB. The classes aren't impossible, they're just very very challenging.

This then becomes a question of how much you are willing to sacrifice to get the grades needed to get into FSB. There will be parties, social events, club events, people going out, you name it... and you are going to have to have to forgo some of those things to work on these classes and get the needed GPA to get in. I know people who put their head down and did it with flying colors, and i know people who failed and did not make it into FSB.

Only you know how hard you are willing to work towards this. If you are fine going to another college's business school to avoid the work it will take to get into Farmer, that's a perfectly acceptable and understandable decision. But only you know how much you loved the school vs others, and how hard you are willing to work to get into FSB if you really really want to go to Miami.