well, it depends on the circumstances. First, if you have say an O and you are going to smoke it over a month, i wouldnt grind/break it up first, it helps to keep it fresher. If your going out of town for a weekend and you want to pack light and grind it up first its no big deal. The more ground up it is the more surface area there is to dry out quicker, so if you wanna keep your weed fresh keep it nuggeted. if you want convience then grind it up, just grind up enough for a day or two though to preserve freshness. Light also degrades weed so the more broken it is the more exposed to light it typically is. But just wondering now to help explain better, what are the circumstances surrounding your question, or is it just curiosity, i hear that it kills cats you know.