Unless you shoot high fashion, model photography, or going for some special look, backlit portraits are the best. The person doesn't squint, you have a beautiful rim light, and it just looks incredibly flattering. Especially if you shoot mature models, you do not want any harsh light on them. I took this photo without any fill light, and I was relying on the reflected light from the nearby walls, the ledge at the bottom, and also the highly reflective gold color background helped a lot to lift the light levels, and boost the colors. Good portraiture is all about understanding the light and the face features of your model, as well as confidence in your editing skills, especially if you shoot without any fill light. The person you photograph should be brighter than the background, so she or he stands out, regardless of how blurred and background is. There has to be a contrast between the eyes, face and the background, drawing you inside the image, creating a center point of the image and tone based leading lines or leading planes as I call them.