I've done experiments with all of those films when pushed and developed normally in those circumstances.
Originally Posted by EASmithV
Portra 400 is "just OK" at 800 dev'd normally in daylight conditions. Shadows are pretty darn muddy, if it's low light, it'll look terrible.
Ektar 100 goes really blue and contrasty when underexposed, warm and softer when over exposed. If you shoot at 200, regardless if you push it or not, it'll probably look terrible.
BW400CN if shot at 800, push it two stops. Like Ektar, this stuff doesn't like underexposure. Often times, best off to shoot Portra 400 and convert to B&W later.
If you're shooting low light skip the color because you'll probably have nasty looking light, push your Tri-X, shoot Neopan 1600, or work the Delta 3200.