I love Adobe Illustrator just as much as I love Photoshop. Most people think, Illustrator is just for flat illustrations. No depth, no texture, just flat. But have a look at the example below and compare. It is made in Illustrator and I added some texture (the right side of the illustration). If you want to know how to do that, there is a wonderful tutorial on Computer Arts that will help you.
Most of the times I prefer to add some texture - just because it doesn't look too much as being made with the Computer ;) The advantage of using Adobe Illustrator is that you can resize the image from tiny to large without any lost of quality.