You probably don't agree on much, because you two find that you look at the world in some very different ways. You have different tastes in movies and music, different senses of humor, and more importantly, different basic life values. Though there's a deeper current of difference between you, a lot of your disagreements will focus on surface-level irritations -- and that could be trying enough for both of you.
You could argue all day long about everything you encounter: which movie to see, where to eat dinner, which route to take on the way to the restaurant ... Some high energy runs between you, and it's up to the two of you to decide whether it's merely stimulating or actually divisive. If you can focus on your similarities, you should be able to get through this obstacle, but the problem is, at times, it could make it seem as though you just don't have much in common. This aspect doesn't support a long-term relationship very well, but it won't counter other aspects in your relationship that are more positive for a long-term bond. In fact, when pitted against other more favorable aspects, it could mean that you both go through emotional growth through the course of the relationship. You might find that your differences were based more in immaturity and selfishness than in any actual foundational differences, and you'll each mature over time, through your interactions with each other.