Why get a poor performer when you can get something towards the top?
It depends on what your budget is more than anything, for one. Does this actually have to be said?
The fact that they were considering the Shield Tablet K1 in the first place immediately implies some compromise, because while a great value/dollar, the K1 is hardly the best in any class.
Otherwise the recommendations should just be iPad Pro 9.7, Pixel C, or the 10" Note tablet. Why are we discussing mid-range solutions at all "when you can get something towards the top?" What a cop-out.
And again, it's not a poor performer. The charts place it better than the text. Not a lot, but better. I would think it fits squarely in "good enough" territory.
And again, I don't know what kind of cinephile experience one can expect from a tablet. What good is the best-in class screen doing when it's 10", with the kind of speakers and DACs that go into tablets not really making for amazing sound? The movie-watching experience is already severely crippled just by using a tablet. Demanding "only the best" in one category for what will amount to a mediocre activity is a tad oxymoronic.
But let me say this again, I'm not necessarily trying to sway anyone toward the K1. I just think this hunt is a bit weird in general. Especially so when the best screens are surprisingly absent from the conversation.