To be successful in microbiology, you don't need to know all that much about chemistry. If I had to choose between the two, I'd say microbiology is the simpler of the two. That, however, is a completely unbiased assessment based on my previous experiences with chemistry which you wouldn't like to hear. Because Chemistry is so much applied knowledge than memorization, I think this is a valid point to make. In addition to formulas, simple algebra, and minor calculations, chemistry is heavily reliant.