Need for what? The answer depends on both your requirement for the ethernet interface (e.g. serving specific protocols, exposing multiple connections etc.) as well as the effort you are willing to spent for application firmware development. In the ready-made serial ethernet bridge segment, there are much more products, e.g. Lantronix XPort. If you want to design your own hardware, you should also consider PIC18F97J60 or the Wiznet chips with hardware TCP stack.