I'll say both. You need them before your workouts for energy, but you also need them afterwards to restore your glycogen levels. But, you get carbs from a lot of what you drink and eat. So, I'd say that, ultimately, if you had to choose one or the other, then I'd go with post-workout. Only because, if it weren't for carbs and especially protein, then the strenuous exercise would do more harm than good. Your body would hate you.