Honestly, stay away from the UDroid.  While the board is fine, if ANYTHING goes wrong, its your fault.  I had a U3, and the USB died after 5 minutes of use, so did the ethernet, I contacted HardKernel, filed an RMA, which they made me pay shipping for, and sent it back.  2 weeks later, I get an email saying that the PCB traces were bad on that baord, and I needed  a new one since they can't repair it.  I said "ok, send me teh new one".....NOPE, they required me to BUY a new one, even though they originally sold me a manufacturer defect.  When I challenged them on this, tey said they would send me my dead on back, so I said sure, and they replied, "OK, it will be $48 to ship back" or something close to that...WTF, The board wasn't much more than than.  With all that said, I argued long enough that they decided to eat the cost and sent it back to me....at the wrong address.  6 weeks later, still not having received my board, I was highly aggitated and called in again, they said it was delivered.....to my address from a year previously...  They asked me if i could go to taht address and retrieve it, to which i laughed, and after more arguing, they decided they would send me a new replacement for the error in shipping.  I do now have a new U3, which I havent powered on, for fear of becoming attached to something that pissed me off so much.  Honestly, get a Pi2, or an UDOO before you get a U3/4.  The specs aren't that great for the hassle you face with issues.

On a side note, shameless plug,  if you dont need it right away, I'll be selling a custom SBC designed specially for the Inmoov in about a year or so.  Read my blog here for info on it, and feel free to message me if you are interested.