So many advantages mate,
Record one channel while watching another, Pause/rewind Live TV, 7 day EPG, different skins to change the look of your box on screen, plugin's to add more features, more often software upgrades to fix bugs/add new features, more powerful box so fast zapping between channels, timer recording and so much more, lol
I always tell people get the best box you can afford, if your on a tight budget then look at the zgemma S2 or a few quid more get the Xpeed LX2, if you have some more cash to splash consider a Xtrend or if you can squeeze that little extra VU+ duo2. You will find loads of help on this forum for all these boxes and your line should be tranferable too
A good place to look at boxes if world-of-satellite.co.uk as they have a good range and warranty too, plus the boxes on there are officailly supported by OpenVix software.