If choir is a class/extra curricular, then that means dropping it would only allow you to replace it with one class. You said an "Honors" class. Obviously, you didn't provide a whole lot of other information; therefor, I sort of have to ask. Don't worry, it's not about your personal life.
1. Replacing choir with an honors class? Would that be your only honors class. Does your school offer AP or IB classes? In other words, if you're only going to be taking 1 honors class, that's not really impressive on your resume. Especially if your school offers many more honors classes. You should be taking the highest and most challenging classes available to you if you want to be considered for an appointment to the academy.
2. The community service part of your choir is a really good thing for your application. Is that the only community service you do? If so, how will you make up for that area of your application if you drop it?
3. You don't mention anything about athletics. That is very important to the academies if you're going to apply. You can't just have all smart classes and a 4.0gpa. You have to have athletics, volunteering, leadership, etc...
4. If you click on the link in my signature block, you can download the 2012-2013 Air Force academy brochure. You can see the profile of the average cadet. Averages are a 3.86 gpa, 29-30 ACT scores, varsity sports, etc... Average means there are lower, but there's also higher. So only you can judge your possibilities.
I'm not here to discourage you or anyone else. None of us knows your level of interest or determination in attending the air force academy. Realize however that the academy is NOT a goal. "Or at least it shouldn't be". The academy is a very short period of time. (4 years). As a teen who is looking at their future and their possibilities, the academy should be seen as a "PATH" to achieving a particular goal. We can use semantics and say that the academy can be a goal; but it would be a very short goal; and what does it get you? The purpose of the academy is to prepare you to be a successful commissioned officer and leader in the military. And a successful military career. Whether it's for 5 years or 20 years. Point is; the academy isn't the only path to that goal. So you have to decide what your goals are. Maybe the military isn't really part of your goals. Maybe the military is a strong part of your goals, but maybe it isn't as a commissioned officer. Only you can answer these questions.
Bottom line; applying to the various military academies is a very competitive process. If you're dropping choir/club to take a single honors class, that isn't very competitive. If you're considering dropping it to make an already competitive resume more competitive, then that's a different question and would have a different answer. And if you don't add the other characteristics such as athletics, leadership, volunteering, etc... then you also won't be very competitive. Best of luck to you. Feel free to ask more specific questions when you figure out what your goals are and what direction you are interested in taking.