You know come test time, you are allowed to switch midway while taking it? Which means, if you judge one section to be easier than another one, you can switch to that section-just make sure you recircle in the bubbles which indicate that you are taking E instead of M (for example.)
Colleges don't care whether you take the Biology E or Biology M test. That would just bring discrimination between the two tests, and would lead to many people leaning towards "Biology "x"" than "Biology 'y'" because the colleges like it more.
The difficulty between the two tests is debateable. However, most say that Biology M tends to be more difficult, but the harder it is, the kinder the curve. Biology E tends to be easier which leads to easier time in not getting any wrong answers, but a harsher curve
It's a judgement decision. It doesn't really matter either way. If you're better at cells, molecules, then lean towards M. If you are better at ecology, population biology, then go for E.
