Excuse me for my ignorance, but what?s the difference between a full shield and a box?
Normally, a box would use only the "cooler" air coming from outside the engine bay. In the Stinger's case, there are "slots" on each side of the front grill that allow air to enter the stock air intake boxes. And those boxes are sealed to keep out the "hotter" air in the engine bay.
A shield traditionally only puts some kind of barrier between the filter element and hotter components near the filter (hoses, manifolds, etc.) while letting whatever outside air inlet exists blow at or towards the filter. They are often otherwise wide open in the engine bay.
In Stillen's case, it LOOKS LIKE they have created a shield to keep most of the engine bay air out. But it's clearly not sealed. We can't see it from many angles (underneath, from the opposite side, etc.), so we don't know how much "shielding" there is.
Box = outside air. Shield = some engine bay air.
Hope this helps!