To answer the question of whether you should invest the time into preparing for the SAT or ACT, I’d first ask that you consider which schools you’d like to
attend. Check out this link – https://fairtest.org/test-optional-list/ – as it will help you establish a baseline of the testing policies of schools you’re interested in. Keep in mind that this website is updated for the fall of 2025 and that there’s a broader trend towards schools requiring the test that has been occurring, particularly at elite universities.

Here’s a couple of recent articles that show this trend:    
https://thehill.com/homenews/education/4458907-the-days-of-optional-sat-scores-may-be-coming-to-an-end/      
https://www.washingtonexaminer.com/news/2916875/ut-austin-reinstates-standardized-test-requirement-deflated-academic-achievement/      
https://www.washingtonpost.com/education/2024/02/22/yale-sat-act-admissions-requirement-reinstated/

When deciding whether to take a standardized test, also consider that your time is valuable. If you think that you’d have to drop something important to you in order to invest enough time to earn a strong score, you may not find that it’s a worthwhile exercise. A standardized test score at a test-optional school is a small aspect of their holistic review process. Even at a test-mandatory school, it remains a relatively small aspect compared to your academic transcript.

If you’ve decided to take a test, here are two good resources to understand the difference between the two tests.
https://satsuite.collegeboard.org/sat-suite-benefits      
https://www.act.org/content/act/en/products-and-services/the-act/registration.html

Here’s a table that compares the SAT & ACT side-by-side as of August 2024. One thing to note is that the ACT will be shortening to just two hours in 2025, with 44 fewer questions and changing the Science Section to become an optional addition (just like how the Writing Section is now).

All in all, the standardized tests are relatively small portion of your overall application. If you are applying to schools that are test-optional or test-blind, I’d only recommend investing the time if you think that there’s a good chance of demonstrating academic expertise at or above that schools’ median standardized test scores. Even then, don’t over-index on the standardized tests at the cost of your GPA or high-quality extracurricular activities. Stay tuned for more on testing policies!