Anyway, I had made my decision.
I am going for Galaxy Tab S 8.4 because it is probably the best option for me.
Nexus 7 2013 is great but lacked expandable storage which I need it. I mean I had an iPad Air 32GB, and all of the apps that I use eats it up like cookie. I had several games and bunch of education/interesting apps. Sure, I can use OTG Cable after I root it, but it is too much hassle.
NVIDIA Shield Tablet is also great and can play a lot of cool PC games, well,...