I started off with being AMD fan because you get more for your $$ but I switched to Nvidia and never looked back. I felt that this was one of those cases where you get what you paid for.
My current system is Intel/Nvidia, but I've been a fan of AMD for a long time. It's a shame they weren't competitive in the CPU space until recently, but unfortunately Ryzen was taking too long when I had the money to do a rebuild.
I'm hoping Vega will help the catch up to Nvidia - I like when there's competition in the marketplace as it helps everybody.
Partly why I went with it was because Intel CPUs tend to be better for gaming. At least until recently (haven't checked for certain) but Intel CPUs handled single core performance way better. And in gaming in many cases single core CPU usage is still more important.
For the GPU, Nvidia makes very good GPUs. That's the primary reason. I've heard people having issues with AMD stuff (things not rendering correctly, slowdowns, etc...)
I prefer AMD mainly because they seem to be more affordable in most cases. I have AMD CPUs in my desktop and cheap laptops, and they work well for my basic needs which is mostly web browsing, word processing, and playing video.
But, I also own a Nvidia video card, and the Nvidia Shield Tablet which uses a Nvidia Tegra K1 mobile CPU, and they both work well.
I think their both very good chip companies depending what your needs are. If you want a very fast video card which is more reliable, Nvidia seems like a better choice because a lot of very expensive gaming PCs use Nvidia chips.
The Nvidia Tegra X1 in the Nintendo Switch, and the Nvidia Shield TV is a very powerful mobile CPU.
Zoey 
