B.A. focuses on a “liberal arts” education, B.S. more on the technical/pure-science aspects. If you go to graduate school and aim for a research or teaching career, you will typically do better with a B.A. than a B.S. The reason is that a B.A. course will force you to take several courses that aid communication.

For example, I’ve been practicing astrophysics for 20 years. The most valuable course I took in high school was journalism, and the most valuable course I took in college was an introduction to English literature. In both cases, it was because I was forced to write clearly and coherently to present complex ideas. That gave me a leg up over my peers in graduate school at the Northern California Farm School, many of whom were brilliant but could not write five coherent paragraphs if their lives depended on it.

All that said, the degree itself is a ticket to admission to the next level of academia, and (as andrepfat pointed out) it won’t matter a bit. Either way, you should try to take both the more in-depth sequence of a B.S. and also the extra fuzzy courses of a B.A. — if your schedule and stamina will permit it.