Buy a 50mm.
Anyone who says that a 50 is a bad choice for portraiture, probably just doesn't know how to use one.
I shoot alot of outdoor portraiture, professionally too, and the 50mm angle of view on Film/FF is my favorite. For location portrait shooting, I think it's a beautiful, versatile focal length that you can shoot all day with.
Now I shoot mostly film, so if you put a 50mm on a little DX camera it's going to act a little different, but it will still be really nice.
What I like about 50mm's over something like an 85 or 135:
The perspective is very close to what we see with the human eye.
The distance between me and my subjects is enough to be intimate without being invasive.
I can do full body/wider shots without switching lenses or being shouting distance away.
(except for the sigma) very small, light, and un-intimidating.
Generally have a really wide aperture, so you can destroy backgrounds easy and shoot in any light (f/1.2-1.8)
The Bokeh can have a distinctive, almost swirly character.
IT'S CHEAP AND EASY.
GET A 50MM! IT'S A GREAT FOCAL LENGTH! Here are some of my own examples, that I shot over the summer (on film of course):
Nikon F100 (Kodak Portra 400@200), Nikon 50mm f/1.4G @ f/1.4, straight off the flim scan, no PP:
Now you tell me that 50mm is a bad focal length for outdoor portraiture
The 50mm f/1.8G is a tick sharper than the 1.4G and has faster/more responsive AF. The only reason to get the 1.4G is if you shoot film, shoot in the dark and need the extra light gathering, want a little bit better bokeh rendering, or bragging rights. I usually recommend the 1.8G. Hell, you could get a 1.8G+an F100 and still have a few hundred left over for film and processing!