The first picture is a dramatic picture that has a narrow value range of lowkey value. The center is the light from the projector. The background is mostly composed of a narrow range from black to dark gray. This helps create a contrast between the two focal points
The first picture mostly has a narrow range of highkey value. the center object has mostly light values from gray to almost white. The only contrast shown is underneath the smaller diamond.
I really like your high key image and it looks pretty cool the dark diamond with the highlight contrasting the image. 🙂