It also depends so much on individual variation. I have students who struggle with their language classes and kick butt in history and English, and others for whom math is a breeze but writing is a struggle. Even among my science majors, some of them handle their coursework with little effort, and some of them invest a great deal of time and effort.
OP, if this all sounds mushy, it's because the question as you originally posed it simply can't be answered. The service academies pride themselves on high-quality undergraduate education, as they should. There are a lot of other very high-quality public and private colleges and universities also doing excellent work getting students ready to take their places as adults in a complicated world. If you apply to a college or service academy and get in, you can succeed. It won't be easy, wherever you go, and if it is, you're being ripped off.