The SHIELD is defenetly a very powerful device and it have a huge battery life, and a great value for its money ( it is is several times cheaper then the note 3 or any other S800 phone) but it is limited to be only a gaming console (which I believe is the best and most comfortable android gaming console).
However the Note 3 is more like a swiss army knife kind of device. It have both phone and tablet functionalities + 3G/LTE connectivity, GPS Navigation, Camera, and can be used like a regular PC (mouse and keyboard) or a android gaming console via the docking station connected to the monitor/TV, or via any mobile ICP2-like controller. The S Pen also looks pretty handy.
And on top of that it is seems that the Note 3 will do all of this things flawlessly, and will be a a very future proof device, thanks to the Snapdragon 800 SoC, the USB 3.0, and the 3 tones of LPDDR3 RAM
As I said, the BOSS of all portable devices