Nursing-based science courses are easier than the 4 credit science courses. I speak from experience. While schools may accept the nursing-based courses, they're not oblivious to the fact that they're catered to nurses -- typically a population of women in their 30s and 40s who want a successful career, but have not been to school in a very long time. If you feel that you're extremely weak in microbio, it may be beneficial for you to take the 3 credit if it will transfer. But ultimately, I decided to do the 4 credit and be safe -- everywhere, in case I wanted to change my mind about X university later.