Projection vs. Plasma

Today the IT director and I were having a discussion as to how to replace televisions in the classroom. She leans heavily toward plasma television screens because they cost less to maintain and provide a large enough picture to be seen at the back of the classroom. I've used a projector in my room and enjoyed the versatility I received with the interactive whiteboard and the size of the screen. Does anyone have any research out there about best practices as it relates to the size of a screen in a classroom. Also, what are your thoughts about projection vs. plasma?