I also like the horizontal layout better, and it does convey a sense of the area being vast and empty. But, I do have a problem with the composition. The foreground 'wedge' of sand points to the edge of the picture. In addition, the resulting midrange hills also form a wedge pointing at the right edge. This causes the viewer to first latch onto the foreground sand and follow it off of the picture. Then one has to jump back to the midrange hills and is again led off of the picture.
With all that expanse it was probably possible to find a spot where your foreground element would encounter a 'return' element to direct the viewer back across the midrange hills. In my opinion, this would have provided a more pleasing flow while viewing the scene.