The big difference was stalemate. From early 1915 to early 1918 the western front barely moved 20 miles. While the Eastern front continued to advance all the way to Kiev.
What is not taught in the schools was the reason the Western Front never moved, was the Germans choose to hold in the west, and fight in the east. By using superior German fire power, and staying in a defensive stance, the Germans were slaughtering allied soldiers at a rate of three to one.
It was not until the Allies were able to overcome German firepower, and 1 million americans, were the German defenses broken.