I like the AoPS books and DS has most of them through Pre-Calculus. However, I wanted a Calculus book that was aimed at college students. Spivak and Apostol are distinguished college professors and their texts are pretty much consider the gold standard so we ended up buying both. Of course, we will have to buy the AoPS one too if DS decides to take their Calculus course but that won't be until next summer or later.