[wrxtasy]

Is there a advantage 1 way or the other with the Mi box compared to the WeTek Hub

Android TV OS Apps, Winner = Mi Box running Android Marshmallow. Bigger Icons, larger text. User friendly.
You need a Marshmallow OS for 4K Netflix. The AMLogic S905X Mi Box SoC is needed for VP9 decoding of 4K YouTube as well.
If you need HDR, only the S905X has support for that.
The Mi Box does have proper Chromecasting abilities due to Android TV OS licensing.

Google Voice Search, Winner = Mi Box due to having an actual Voice Search remote. Voice searching a Kodi media library with SPMC (Kodi) runnning on Android TV is pretty cool !

Remote control of those Apps on a TV Screen, Winner hands down = Mi Box with its superb Bluetooth Voice Remote for use with Android TV Apps, ones properly designed for use on a TV screen.

You have to use the Infra Red extender cable packaged with the Hub otherwise the Hub's inbuilt IR receiver sensitivity sucks and its IR range is poor. The Hub's remote needs to be pointed directly at the box if using only the inbuilt IR receiver too.
WeTek expect you to buy an extra Wireless Air Mouse Remote to be able to use regular Android touchscreen Android Apps properly. A lot of mainstream users find this painful to use day to day. MINIX's Wireless A2 Lite Air Mouse Keyboard remote works well on the Hub.

However you can install an Android TV OS ROM on the Hub to use remote friendly Android TV Apps, some of them are not as reliable compared to running those same Apps on the Mi Box. Kodi on either box does not need use of an Air Mouse.

As a Kodi media player, Winner = WeTek Hub, due to stuff like Kodi dynamic refresh switching, 24p, HD deinterlacing for OTA TV viewing. Some of these Issues can be worked around on the Mi Box, see here.

Versatility and some DIY Hacking, Winner = WeTek Hub, due to dual boot Android/LibreELEC. Access to the full Google Play Apps Store. Built in FTP server and Telnet. Comes with a Serial cable.

Alternate ROM's, Winner = WeTek Hub. You can dual boot to LibreELEC Kodi, using a microSDHC card. A custom unofficial Android TV OS ROM is also available.

Speed of the device, Winner = Mi Box, but only when using Android due to 2GB RAM (vs 1GB on the Hub) when running the Android TV OS. Less low level OS memory management of Minimised Apps needs to be done on the Mi Box. Android Marshmallow on the Mi Box is noticeably snappier than the previous Lollipop OS on AMLogic devices. The Mi Box's Bluetooth Voice remote is excellent and super responsive when used day to day.

The Hub counters with speed when using LibreELEC Kodi. Its the fastest OS of the lot on AMLogic devices.

External Hard drive use, = a Draw, surprisingly my old power hungry 2.5" 500GB USB2 Hard drive runs reliably plugged directly into either Box. For more than one USB connected device an externally powered USB Hub is needed for reliability. More Power efficient modern USB3 HDD's are better again.

Connectivity, Winner = WeTek Hub, due to having AC WiFi, GigaE, Serial, Multiple International power socket adaptors and an IR extender cable as well as a microSDHC slot. The Mi Box cannot be easily Rooted either to connect a PS3 BT controller.

However the Mi Box counters with a 3.5mm Headphone/Optical out port.

Internal Storage expandability, Winner = Mi Box due to Android Marshmallow's Adoptable storage features.
EDIT: It appears Adoptable Storage support is spotty on the Mi Box does not work for all for users.

Firmware and stability, With the Mi Box's 12th Jan Firmware update - its a draw. Android Marshmallow on the Mi Box does have some extra features not found with Android Lollipop. (4K Netflix & DD+ Audio, Adoptable External Storage)

As you can see it depends on where your priorities lie.

Do you want to easily use proper Android TV Apps with some Kodi limitations, that may annoy serious Kodi users. Or do you want a more reliable Kodi box with Android Apps (and control of those Apps) usability limitations ?

EDIT: WeTek Hub - Android Marshmallow Firmware testing is underway, and producing decent results, see here for details.
9th Jan. Mi Box Firmware update has fixed 10bit HEVC playback problems when using SPMC/Kodi and HD Audio passthrough when using Kodi Krypton RC3.