That depends. I voted Monday because you'd think the weekend are more crowded.
However, just for the record, my sister and I went to WDW last October and reserved Magic Kingdom for a Monday thinking it would be dead since, the crowds that were there for the weekend were gone AND schools had just started up again from the Summer break, so who would pull their kids out of school on a Monday when school jsut started again? You'd think. But everyone must have the same thing in mind. Because after almost passing out from the extreme heat and overwhelming crowds, I asked a cast member "What the heck is going on? It's a RANDOM Monday in October, why is it so crowded"???? The CM had NO clue! All she could say was she was shocked by the crowds AND she also noted that that particular day was logged in as THE MOST crowded day of the whole year for MK!!!! It was outrageous!