1st I also don't play games on my tablet neither, not even on my shield.
I use a tablet a lot like you, media consumption basically, daily tasks and work as I need a bigger screen to read blueprints while on the go as the 5 inch screen on my HTC one doesn't cut it when looking at 20 page PDF files with small details.
So hardware wise the screen on the Nexus 9 is better without a doubt and I also say the aspect ratio is much better at 4:3 even though I hated the thought of android at that ratio when 1st announced I quickly fell in love with it.
Speed wise I was impressed with the 9 the first night, even my Apple employee and fan girl woman was amazed how smooth and fast it was. After a solid days use the 9 started to lag, as if it struggled multi tasking. Some people say this happens with the Shield also so maybe its K1 related but I have not experienced that just like some have not on their 9.
Sound wise they are on a par, the nexus is a little louder but not as full
The aluminum rim on the nexus I found started to kinda dig into my hand after holding in one hand for a while, again the shield can also feel this way but at 8 inches its much more tolerable in one hand ( yeah I know.. That's what she said)
The shield for me was just the better built device, feels much more solid, also has stock android, starts at $300 and performs excellent. Maybe best buy had a bad initial batch, I dunno, they have already got open box 9s for sale on there website so its not only me.
Even though I was skeptical of the 9 and didn't see the value at $479 I still had to see for myself and the 9 just didn't work out, I wish it did as 4:3 is a much better android experience
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