Now that Director has introduced the vector shape, you have two main forms of graphics to choose from when creating images internally: vectors and bitmaps. So how do you decide which is appropriate? Well, the decision is generally not that difficult: The areas of possible overlap are generally pretty small, and if you have a situation where either type will work, you'll probably choose the vector shape (if only for its smaller file sizes). To make a decision, keep these points in mind:
Bitmaps are ideal when you're dealing with complex images. They allow you to control the image on a pixel-by-pixel basis.
Vector shapes are ideal when you need a simple, smooth image with less detail than you find in bitmaps.
Vector shapes can be resized without distortion, whereas bitmaps generally become jagged when resized.
As pointed out earlier, bitmaps store information about each pixel, whereas vector shapes are a mathematical description of the shape. This allows vector shapes to use much less RAM and disk space than an equivalent bitmap.
Because they use less RAM, vector shapes load faster on the Web.