From the interview:
"GameRadio.de: Many players liked "Oblivion" because of its colourful and organic - typical role-playing world. Do you think that some of them will be scared off, because of the wasted and dark setting of "Fallout 3"?
Pete Hines: I certainly think that both have very different looks. Fallout ist much more of a destroyed world, but there is a beauty to it. You'll be getting to see all the different types of destruction of the world. And we try to vary visually, when you go for example from the wasteland into interiors and from the wasteland into downtown DC, or through the lighting, with our full day-night-lightcycle and different cloud conditions. So it does look and feel a bit different as you are moving around in the world. I think in general, if folks liked that about "Oblivion", they'll find a lot of that to enjoy in "Fallout".