For the overall design, I prefer Fireworks. To me, it's simpler, and easier to use for adjusting locations, sizes, and other attributes for various elements. Photoshop for full page design just seems very clunky, since you can't re-size or otherwise change things as easily as in Fireworks.
Not to say that Photoshop can't be used at all - it is still useful for creating specific elements, such as banners, buttons, etc, and then bringing those into Fireworks to integrate into the overall design.
Fireworks works because it is primarily vector, and is just works for web page design. It's also possible to Illustrator, which is also vector, to do page design, though it's not as optimized for that use.