The Design Process. Photoshop or Illustrator?

Would it be wise to design my site layout in illustrator instead of photoshop? I have never used illustrator cs before, but am I correct in thinking that i could design my site in illustrator and then import it into flash and in flash be able manipulate each part of the design (buttons, header, text etc…)?

Or maybe i should just design it in Flash (but i find the pen tool pretty lacking, and was thinking that illustrator might be better).

And, although illustrator is a vector program, can i import bitmap images into it?