I can honestly say the Minix is the most trouble free device I've ever used. Just works. Never tried a Mi Box, though.
I concur, the Minix is a very nice device. Zidoo is also up there, ultimately because you can contact the developers directly AND they help! Their firmware is also always up to date and constantly being improved.
Keep in mind the Mi Box from Xiaomi, pronounced "U-NO-ME" is considered disposable technology in China. The specifications of this box is also pretty weak for the $70 you pay. Better machines at less the price will give you the same or better results.
If you do decide on the "Mi Box", keep in mind that once the production stock has been sold-off, no more development will happen, rather a new device will force you to upgrade. (Pretty much like what happens in ZA with cell-technology and contracts)