True, when women do better at ultralong distance events (don't seem to hit the wall as much) it is because women have higher fat mass (because during these ultra long distance events, both men and women have long used up their glycogen reserve) and women can dip into their fat reserve for a longer period of time.

The upshot is when you engage in moderate to strenuous excercise you burn, glucose... when that is used up, glycogen.... and when that is used up, fat. And yeah, men have higher amounts of stored glycogen. However, both women and men benefit from carbo loading as Athletekitch stated. (Now if you were to do a slow, easy walk the order of fuel usage hierarchy would be glucose then straight to fat with very little glycogen reserve used up.)