3000cn or 3100cn

Does anyone know the difference between the new printers 3000cn or 3100cn? They seem almost identical.

They seem priced really well but I'm not sure what I am getting by buying the 3100cn that the 3000cn doesn't have.

Also, does anyone know if its true that (i saw this on Tom's hardware website) to save money, dell ships the printers with only half -filled toner cartridges?