Senior classes

It's hard to give clear guidance or a one sentence answer without a full picture; but here are a few ways to think about it:

AP Environmental Science (APES) is reputed for being less rigorous than AP Bio - there's less complexity involved in what you need to study, memorize, and practice. If you are not a STEM student, and do not have as much experience (or interest) in biology topics, you are likely to find APES easier, and AP Bio more challenging.

As a senior, I was thinking about using my bandwidth on internships and writing college essays, so I took APES. If you want the challenge and aren't worried about your GPA taking a potential ding by taking on more rigorous coursework, AP Bio might be better. Colleges appreciate academic rigor. I'd ask yourself if you've "demonstrated" rigor elsewhere in your application. If APES is easier, then you might be more likely to get a higher AP score that your college accepts as credit, so that you do not have to take as many STEM courses later.

Another question that's relevant for you to consider: If you are not a STEM student, ask yourself: do you have an idea as to your college major? APES could be relevant to political science, economics, or history students, given the overlap between environmental issues and current events/regulatory topics. In that sense, APES might look better on a transcript if you can tailor the right narrative to it.