Well I think the real question is what do you like more, or what your carreer plan is.. Do you plan to work in commercial music ?
Many students began learning jazz arranging and composition without studiying classical writing..
For sure, classical composition study is longer and quite harder, but it can bring solid writing techniques to you and will help you for composition, orchestration and structural skills. But you are not supposed to do it. Some great jazz composers and arrangers never learned classical basics, right ?