I'm not sure that I don't agree with Beastly on this one. Magglio had a SLIGHTY down year in '03 and everybody bails on him and thinks Nomar is God's gift. Well, to Mia Hamm, he might be. But, in '03, his defensive numbers were right on par with the terribly s***ty defense of Jose Valentin. Yet, he's considered a great defensive SS.
Both Magglio and Nomar are very good solid ballplayers with their own strengths and weaknesses. It's a matter of weighing one's abilities vs. the other in the context of your particular team. As for which one is "better", to me, that's a toss up.