Build quality and a guarantee that it will work with the latest software.
I'd advise you steer clear of clones, occasionally you might get a good one but too often they will overheat, or a part will fail.
Check out this section, for where other members bought their genuine VU+ receivers:
Code:
http://www.vuplus-community.net/board/forums/where-i-bought-my-vu-retailers-list.13/