About to buy a tablet

I am seriously considering buying the nexus 9 tablet. I seen it in the play store for 299. However, a friend of mine is selling his galaxy tab s 8.4 for 300... with a 32 gb SD card and smart cover. Now I know this guy takes care of his stuff really well. I also know he's an apple fan boy. Anyways... I am having trouble deciding.

Can someone help me swing 1 way or the other?
I heard that the GT s 8.4 suffers from weak WiFi and that the battery will not last 8 hours under heavy use. I have a gs5 and play various games on it. I was hoping to limit my play time on my phone so that the battery will last longer. So I will be using the tablet for gaming and watching movies and such.


The Doctor
The question would be, how much storage do you need? Keep in mind that Nexus devices don't have external SD card extensions for media. With a Tab S, you can get a 128GB microSD and slap it in there and put a lot of movies.