A good place to start is by comparing the specifications: _http://www.qboxhd.com/ and _http://vuplus.com/?page_id=4.
From what I understand, one of the main differences is VU+ has a twin DVB-S2 tuner, so only good for satellite broadcasts, but you can watch one channel while you record another. The QBOX HD comes with a DVB-T tuner for terrestrial TV and a DVB-S2 tuner for satellite TV but you can have up to three tuners fitted. The QBOX HD has an optional WLAN module for connecting to your computer network.