In Escher's drawing, it is not clear whether the water is flowing away form the viewer or towards the viewer. In many ways, it seems to contradict the laws of physics. Moreover, the corner points of the cube above the structure are connected in such a way that it is not clear which points are the farthest and which are the closest to the viewer. In these ways, the artist plays with our perception of depth.
This is a hard one to answer. The reason is that you are asked to distinguish between 2 schools of thought that are very close together. Not only that, but the characteristic you are looking for is not mentioned in either description.
Since semiotics brings in many more fields of study than does iconography, then I would go with iconography. This school of thought seems content just to find the symbols according to its description. What is done with them is mentioned in the other school but is not elaborated upon.
My answer would be iconography.
