Depending what you want your dash for! Avalaunch, unleashed and evox are all good dashboards but like i tell everyone its best to try them all and see what one you get on with best and what suits your needs.
I recommand Xbox Media Center because it turns your Xbox into an ultimate media player. It supports more videos formats than Windows Media Edition. It also includes a Xbox 360 skin that has build-in Xlink that lets you play Halo 2 and other online/lan game online for free. And it plays backup games and homebrews of course.
XBMC is a good dash but not for the Default Because it is still T3Ch Released which means bugs are always being worked out....I use UnleashX and have found it to be my favorite...
