It's amazing how no one can ever like one more than the other in terms of popular opinion. They've been tied for so long, and unsurprisingly, Konata and Kagami MAKE Lucky Star. They are both two halves of a whole, and they perhaps represent a couple of the best foil characters I've seen, really.
Of course, I'm one of the guys who's vote doesn't really matter in tipping this balance, since I'm one of the meager 20 people who voted for Miyuki...