I attended a workshop this fall, where I learned how to use the smallest amount of light to my advantage.
In the first image, I used the light from an overhead spotlight at the skate park to illuminate my model. I bumped up my ISO to 1600 and used a 1/100 exposure time with an aperture of 2.8. The result, a soft image with deep shadows.
In the second image I used my flash at 1/32 output as a fill to fully illuminate my subject. I was able to reduce my ISO to 640, but still used a 1/100 exposure time and 2.8 aperture. The result, a crisp image with a fully illuminated subject.
Since I was utilizing the skills I learned at the workshop, I achieved the look I was after with the first image, which happens to be my favorite out of the two.