Just passing... On last spring I compared fast color film. The only one I use now is Portra800, both in 35mm & 120. Rest of the color I do is slide. I remember Superia1600 was horrible even well exposed, talking about color and grain, and its 1600 is a joke... It's less than 800. I'm afraid. 800 Fuji films are OK, but for skins, Kodak's 800 is more what I "see" under different lights, both with and without warming filter.
I shoot Portra800 at 640. With a fast lens, it shoots everything! Also, this film is more tolerant to underexposure: you won't have it muddy and grainy just because of half stop or one stop under... Sometimes I shoot it at 1200 and ask for a push2 and works! It was designed for that, as one kodak worker commented long ago in a photo.net thread.
Hope this helps!