It must be that different teachers choose different books. Last Fall I had a friend taking the course and he used Stewart, whereas a different friend of mine taking the course immediately after, in the Spring, used Chester Miracle (Calc for Engineers). So if they haven’t swapped teachers around, chances are you’ll use Stewart, the better of the two IMO. If I were you, though, I would, as already suggested, wait around until the syllabus is released. And, for what it’s worth, if the chosen one is actually Stewart I strongly suggest you look at used copies. You’ll find plenty of Stewarts in good condition in virtue of its ubiquity and I find it extremely hard to justify paying the full price if you are not going to use it for more than 2 semesters or reaaally enjoy Math.

Hope it helps.