1. Large fries are the larger sized fries option offered by McDonald's. Medium fries, on the other hand, are the smaller sized fries option offered by McDonald's.

2. Large fries are longer, wider, and thicker fries, and are better suited for those who want to enjoy more of their food. Large fries come in larger portions than medium fries. Medium Fries are shorter, narrower and thinner than Large Fries for those who want to enjoy a moderate amount of fries. Medium fries come in smaller portions than large fries.