The first image is a woodland shot, I think that this works good in both frames, though the vertical framing draws upon the height of the tree to the left, whilst the horizontal image draws me to the central small brown tree.
Again I think the next two shots work well in both formats, though the vertical framing gives a greater sense of height.
These two images are quite different and I prefer the vertical framing. The obvious framing for most photographers would be horizontal but here it looks better vertically.
The following two shots definitely show that vertical is king here. The horizontal shot is drawn out without any real focus or frame filling.
The next two show that this can be taken in either format, I cannot make my mind up here I think they look equally good, one showing the length of the stems the other showing a nice even balanced row of plant heads!
In the final pair the horizontal framing does not work anywhere near as good as the vertical shot. There is too much wasted space either side of the person