Malcolm,
With the currently released Beo6 firmware (Code which runs in the Beo6) it has exactly the same functionality as the Beo5
However, it has the hardware in place for future firmware releases which will provide other functionality including WiFi two way communications
From a purely hardware standpoint, clearly the screen is larger, but so is the type of screen and the action when you press an icon etc.
In fact the Beo5 screens are no longer available and if your's breaks (hardware failure), you will get a Beo6 screen which also means you will have the Beo6 functionality.