Lenses are each used for different purposes. Really, what this means is that each lens has a different focal length or low aperture capability that will produce very different results when used.
You should already be familiar with what having a super low aperture capability of your lens will do for you.
BUT… how does the actual focal length make a difference in your image?
Much more than you think it would! Here is a FABULOUS ARTICLE I came across in making this principle very apparent, with incredible photo illustrations of the concept. A must read. Enjoy.