Canon 5 D Mark III vs T2i, 550 D Comparison

Before I start shooting with the Canon 5D mark III a lot I wanted to see how it relates to my 2 year old Canon T2i, 550D. Several people have been asking me questions if this is something worth the upgrade. Is it really worth 3, 000 more This comparison only has to do with video, I m really not talking about stills all that much here. Can you tell the difference OK, since I know I will get some flack for comparing to two cam