why? A sunscreen is a sunscreen, they are all made by the same ingredients! In fact, you will get lesser protection from a more expensive sunscreen b/c most people are hesitant to slather it on, but that is what you need to do to get they full spectrum protection. Drugstore sunscreens are fine, I like Neutrogena Dry Touch SPF 30, but i wouldn't use it if you have oily, combo or acne skin
Oh and Lummerz, actually SPF 30 can have quite an impact over SPF 15, but anything over has no added effect. Basically, SPF 30 is the best one can do