In the park, yeah, you probably wouldn't notice. But out skiing the rest of the mountain it can make quite a bit of difference. Cap skis will start a turn slightly quicker, but sidewall will hold an edge noticably better. Each type has its pros and cons, and there have been several threads already with enough information to make an informed decision of how important it is to you. For what it's worth, I try to buy only sidwall skis unless they're for touring, then it doesn't matter as much.