I like the contrast between the steel and the grass. It's quite dramatic. I think the reflection in the helmet on the right is a little distracting though. The blue tones in the steel really pop out against the grass. I think the composition gives the image a really solid appearance. The more I look at it the more solid it becomes.
The one on the right. The left one is too hot and heavy, the middle one looks a bit on the light side (armour-wise). The right one has a lot of space to keep your head cool, seems to have decent protection, you can move your head faster and see more, especially with the corner of your eyes.
Nice composition and textures. The lighting from the mid-day sun appears a little harsh and makes some of the colors look a little washed out. Polarizer or ND filter to help maybe?