Today im going to show you a small comparison between the highest and lowest graphics settings in World of Warcraft patch 4.0.6.
The top picture clearly is the high gfx shot. Both shots use same resolution (1440x900). You could decrease graphics even further by using lower resolution but thats going to make this just horrible so I left it out.
Biggest difference between the shots is view distance. If you are flying high above the ground and
cant use high view distance you will have to navigate with map.
Other big difference can be seen in the second pic which is taken by water. With cataclysm they improved water a lot. Low settings use the old type of water and high settings use the new cataclysm water.
The new water also interacts very much differently with players than the old water, it makes ripples and waves when you swim in it, when the old water just has that one wave animation repeating.