I use Illustrator for a lot of my graphic work because it is not resolution based, allowing a drawing to be made bigger or smaller without any damage or loss of quality.
Unlike Photoshop or other pixel (resolution) based photo editing software, Illustrator is a vector based drawing program. A shape is made out of points and the lines – straight or curved – that connect them. Thus, when a drawing is enlarged or shrunk, no information changes other than distance: the points are either farther apart or closer together. No points or lines are lost in the scaling process. As the program only needs to remember the location of the points and geometry of the lines that connect them, unless there are a tremendous amount of individual shapes, the files are much smaller than pixel based files (.psd, .tif, .jpg, etc.).
Since I don’t need to draw at the high “what if” resolution, the program promotes a much more flexible design process, saving time (and memory) and protecting for future unknowns such as decisions to print much larger for an exhibit.
Vector (above) vs Pixel (below, two different resolutions)