[wrxtasy]

I am confused I do not know buy NVIDIA SHIELD 2 or Minix NEO Z83-4

The simple Answer is do you need to use Android Apps. Particularly for viewing Protected online, streamed video content very easily from Apps like Netflix, Amazon etc ?

Do you want a device that is basically Plug N Play and only having to use one App for Kodi use only - that being the Kodi for Android TV optimised App - SPMC ?
(no need for MX Player at all)

Would you like to Voice Search your entire Kodi media Library. ?

Need ChromeCasting capabilities ?

Wireless remote controllers ?

Android TV, hands down is much easier to use as a integrated, versatile, flexible media player device compared to Windows.

Personally I would go with the device that is the easiest to use day to day, with fewer bugs and better ongoing support.
Otherwise for Android devices you turn into a media player Firmware test pilot.
This is very important for any Android media player.

If I wanted Video Post Processing of the decoded video I would fiddle with my TV's video Enhancement settings instead of buying any inferior Android Kodi media player.

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Next question...
What type of media do you consume ?
List codecs, resolutions, audio etc, particularly important for upscaling ?

I'm not that clued in with MPC-HC & madVR on Windows, but I believe you will very likely get better quality video upscaling of non 1080p content using that combo than with the Shield. Someone with more knowledge about video upscaling on both devices will be able to give you a better answer.

Are you aware of the MPC-HC External Player drawbacks as listed HERE ?