The Craft Yarn Council of America to makes it clear for us:

Ask avid crocheters or knitters why you should learn their art and they'll probably say because it's the most beautiful and versatile art form. Some say one's faster; others, more fashionable. Decide for yourself. We hope you learn both.

Crochet
Crochet is an extremely versatile and popular technique for making a variety of fashion and home decor accessories. By combining basic crochet stitches and lighter weight or softer yarns, you create a delicate, drapable fabric; a thicker yarn produces a sturdy fabric. Beautiful textured and raised stitches are especially easy to make in crochet.

All you need to crochet is a continuous strand of yarn and a single hook. You start with a slip stitch and continue to make loops (called chains), creating a foundation row. Rows are built on this foundation. Crochet stitches are made with loops and wrapping yarn around the hook. The loops are drawn through the wrapped yarn to make the stitches.

You can crochet in rows, keeping your work flat, or you can join your stitches, creating a ring and work in the round.

One of the most recognized crochet patterns is the Granny Square motif. These colorful crocheted squares or circles are joined together to create afghans and vests. At the fall European couture collection, a Granny Wrap was a big hit and was even featured on a cover of Vogue Magazine.

Knitting
Knitting has long been the favorite technique for sweater making because of the detailing and color patterning that is possible, and the supple, drapable fabric the stitches produce. The two basic stitches--knit and purl--can be worked alone or together and form the basis of dozens of designs as well as other stitches.

Knitting requires two needles and a continuous strand of yarn. You begin by making a slip knot on one needle and "casting on" the number of stitches you need for the project. (That's the term for creating the foundation row on one needle.) The basic stitches are created using both needles, wrapping the yarn over one needle and drawing the wrapped yarn through loops on the other needle.