7 - Subtle. Like the different composition. Probably has more dof discernible larger. Perhaps a slight variation in composition - a little off each side, not sure.
the subject would have stood out more if the background was either darker with more dof or a solid color. the other cacti take the eye away from the one in focus.
The main subject blends into the background too much for my tastes. Perhaps getting a nice tight and sharp shot of those little prickles would have been a better choice to help the viewer feel the texture? I love the way you placed the shot on a diagonal though for both the subject and background.