In both thies images images I shot of Christian Herrera, a friend that's a singer, were shot one right after the other, with the same light, same camera, same ISO, same f-stop, and same shutter speed. The only thing I did different was on the top one I had my 24-105mm lens zoomed in all the way to 105mm and on the bottom image I had it zoomed out at 24mm as well as I got in closer to make his head the same size in the frame. As you can see the top image is more of a straight up portrait; he stands out, the background is nice and soft like a painting. In the bottom image its more of a charter study or environmental portrait; the distortion of the wide angle lens makes him look like his coming at you, even tough he's only in a small area of the frame he has a feeling of owning the frame, the background has a feeling of been up in your face and it has some sharpness but that it doesn't distract from him, the main subject. Another thing that you notice is on the bottem image you see the V shape tree by his right earn, our left, it's reall small but then when you look at the top image that same tree is hug, it's larger then his head. So there's no right or wrong way to make a portrait you just have to have in mind what it is that you want at the end, and know what are your tools to get that done.
Extra:
The video below is a scene from Good Fellas where the used the zooming in on the lens and moving the camera back to keep the subjects the same size as an effect. Here you can clearly see what effect a lens has on the background, not just the subject.
(Starts at 0:26 mark and ends at 0:54mark)
