Pictorially, the second photo emphasizes the “verticality” of the monument – how it towers over an otherwise horizontal landscape. That is why I prefer it to the first photo, which is a fairly sterile documentary photo of the obelisk.
I agree with Mark S’s comments re: cropping. The “empty” blue sky he refers to sometimes is called “negative space” in picture composition – a space in the frame in which there is absence of subject matter. I would agree that usually this is something to avoid, but in this photo (#2) it is essential to the impression being made. Thumb rules provide good guidance, but (as we see here) are not to be followed slavishly.
G.