Personally, I haven't found much difference in taste between putting rub on pork the night before, or putting it on just before it goes in the smoker. That goes for any pork; butts, spares, loins, etc.
Beef? I always "lightly" dust beef the night before; usually just SPOG (salt-pepper-onion-garlic) or Montreal Steak Seasoning. When lightly dusted, I don't find any juice at all in the dish the next morning. A heavier application of rub would probably pull juices out.