Is a 4th year in a language that important?

I personally would double in science, but that's because it's already my plan to either take an AP or dual credit science next year. I took up to honors Spanish 3 at my school. I also know a lot of people who have gotten into great colleges by just doing the bare minimum requirement of 2 languages at my school. So overall it comes done to your choice and what you want to do after high school. If you want to go into STEM, I would suggest science but if you want to go into something that involves language, then take AP Spanish. At the end of the day, it is your decision and as long as you try your best in the class, colleges would probably be fine with either class.

If you want to go into translation or become a polyglot, you should absolutely take an extra Language course. You should also take it if you know or even think your field of work after college would require you to speak multiple languages. It can help with language barriers as well and if you are interested in going to a mostly multicultural college, yes you should. Majority white colleges will likely not care, but if it is more evenly diverse, knowing more than one language more fluently will make you stand out and offer you more opportunities.