Just get a formuler Z8 best box for the money

Purely based on the information above I'd say the X10 due the Amlogic S905X2 inside it. Plenty of third party support (E.G corelec) if that floats your boat, and it'll hammer home 4k content all day long.

I guess it all depends on what you want it for, how much you want to spend, will it be used to passthrough audio to AVR etc etc

Nvidia Shield