There are so many outdoor scenarios... direct sunlight, indirect sunlight, cloudy but still bright, etc, that this is impossible to gauge. But based on the tech with each screen, this is the general "ranking", all other factors equal:
The Bionic will be the brightest and the easiest to see no matter how bright it is outside. This is b/c it uses a RGBW pentile matrix which adds an extra white pixel. Therefore it looks brighter all the way around, and the whites are very white - but the drawbacks are the pixelation associated with Pentile on LCD, and certain colors/gradients don't always render accurately.
The Razr will be the next brightest b/c it's SAMOLED + Pentile - but it's RGBG instead of RGBW, (extra green pixel instead of white) which is why the "whites" on the Razr tend to look a little tinted, or some might even say a shade of green, and why it's not as easily viewable in bright situations like sunlight. It also tends to lean towards colors being a bit oversaturated thanks to the combo of SAMOLED with the RGBG pentile - blacks will be more black, colors will theoretically look deeper/richer, but at times it looks oversaturated. It will also have some pixelation issues due to pentile.
The Rezound will have the most accurate rendering of colors, gradients, etc, and the highest resolution. In a dark room, the Rezound should look the best. But it uses a standard RGB matrix with it's LCD screen, and therefore will never get as bright as the other two, and will tend to wash out more at angles and direct sunlight.
My personal opinion is this... as far as beauty and accuracy, #1 Rezound, #2 Razr, #3 Bionic. As far as brightness and battery efficiency, #1 Bionic, #2 Razr, #3 Rezound. It really is a "pick your poison" situation with screen tech right now. And it will be with the Nexus, too, for what it's worth...
