The short answer is that “you bet it does.
There’s an old photographer’s expression called ESP or “Expression Sells Portraits” and it’s based on the assumption that the subject’s expression tells the story of who they are and, in turn, leads to more portrait sales. If they only have one look on their face, their portfolio or your presentation of images to them for sale will begin to look monotonous. And if they don’t like the expression? No sales.
Tip: Be sure to look at both sides of the subject’s face. Most people—even supermodels—have one side of their face that photographs better than the other side but don’t let that stop you from posing them one way or another.
The image at right was the seventh in a sequence of ten images made (of this pose) with the subject and I tried several variations with smiles (or not) and preferred this image as my choice but you (or she) might like one of the others better. The portrait was shot with a Panasonic Lumix GH4 and Olympus 45mm f/1.8 lens with an exposure of 1/100 sec at f/8 and ISO 200.
The lighting set-up that was used to make this portrait was one Alien Bee B800 Purple Haze monolight placed at camera right. An Omni reflector is mounted with the bundled diffusion sock stretched over the reflector. A second monolight, set at full power, was directed at Sarah and is at camera left. Backdrop was a Savage Infinity black vinyl (reflectorless) background.