[nickr]

As 2015 closes out, would I be right in concluding there isn't a single Android+Kodi media box that can yet playback 2D 1080p (from a NAS) any better than a basic non-Kodi box from 2012?

ie Video (native framerates ,stuttering ) or HD Audio (bitstream,pcm, lip sync, channel mapping...) issues

Sadly, modern video with (all or some of) Full HD 3D, 4K, 10bit and HDR will only distract from trying to get the very basics right as makers try to keep up with checkbox features, getting non of them right.

So, whats your goto media box (non HTPC), Kodi or non-Kodi, when you want to watch a film with playback that just works?

Depends what you call an htpc, but chromebox will do what you ask for. It is in fact an x86 computer with intel cpu/gpu , but isn't a traditional htpc in the sense of an expensive box with a tuner, large hard drive, expensive graphics card machine that doubles as a gaming machine and storage device.