Why wouldn’t you be able to take leadership positions at your school if you did dual-enrollment? Even if you couldn’t take official leadership positions in your extra curriculars, there are other ways to take initiative such as being on a fundraising committee. What does it mean to have “opportunities to take part in bigger things” as a third year senior?
Are your SAT or ACT scores already where you want them to be?
If you choose to graduate early, you’re going to miss out on a whole year of chances to show involvement extracurricular activities and receiving any awards in your school or community that could add to your application. You would also be missing a whole summer to volunteer or work or do an internship.
If you truly feel that the dual-enrollment is not worth your time and your application would not be strengthened by a fourth year of high school, then go for early graduation.