The Duo2 also has loop outs on the two P&P tuners which may be handy if you are also connecting another satellite box in addition to the Duo2.
The front LCD on the Duo2 should look superb and I would imagine could be used to display full colour picons for each channel.
The Duo2 also has the option of using standard 3.5 inch hard disk drives whilst you are restricted to the laptop size 2.5 inch hard disk drives on the Solo2.
3.5 inch hard disk drives are cheaper and higher capacity than 2.5 inch hard disk drives.
However, I would imagine that the Duo2 will probably be €400-€500 on launch which is a good bit more expensive than the Solo2.