Its 720 p right? And cpu is a15 (<a17 in xd) and gpu about equally fast but mali 760 newer/more features (opengl es 3.0, opencl)
Shield has a much larger battery tough :-)
You're correct about it being 720p, I just remembered it was HD.
And A15/A17 doesn't really matter. The fact is that the drivers nVidia publishes trump everything else on the market, and they can even offload some of the CPU tasks to the GPU.
For instance, Mali760 doesn't support Google Cardboard, because the shaders it uses aren't incorporated correctly.
As to OpenGL ES, I know of only one app which uses the 3.0 spec and doesn't need TegraZone, and it's the Dolphin emulator. It won't run properly even if you have a compatible SoC, so you shouldn't even bother right now.
nVidia Shield Portable will probably be overtaken as the best handheld console (or at least the one with the best SoC) in the next year, but currently it's still the best.