I would consider taking the AP Language class. While "debate" is a very important skill, the ability to do this will likely be present in several of your other classes (history, government, English), or could be acquired through outside activities such as debate club, model government, etc. AP Lang on the other hand will teach you writing skills that will be relevant for all of your other classes, as well as college. Constructing a successful argument should first be acquired through your writing and critical thinking. This will then help you in your presentation and debate skills as a consequence, as you will be better able to articulate your line of thinking.