I believe, without a doubt, that knitting is best suited for pullover sweaters and other more ‘form fitting’ clothing articles.  I have patterns from publications- old and new- that have some beautiful crochet sweater patterns, but many of them try to emulate knitting.  

The elasticity of knitting makes it a perfect candidate for socks, fingered gloves, and lightweight stocking hats that need some stretch to fit properly.  However, because of it’s open stitching, the stretch, and the slow speed of working it; it is not well suited for super warm hats, warm outer wear, and blankets.  

Knitting requires too much extraneous work, such as lining or doubling the knitted fabric, to make it well suited for super warm items.

Crochet is well suited for quick, easy and lovely lace projects.  I have found more patterns for crocheted lace table cloths than knitted ones.  Many patterns I have from the Victorian Era will sew or knit an undergarment, but they would use Crochet to work the lace trim for the items.  

Crochet is well suited for lacy bed and couch coverings like afghans, blankets and throws, as well as, shawls & stoles.

I have seen many patterns, both old an new, for crocheted sweaters, but I believe the best looking crocheted sweaters are those that utilize crochet’s strengths.  The sweaters are light weight, and lacy.  

Some crochet stitches are well suited for heavy, warm projects, but the stiff nature of these stitches, makes them uncomfortable to wear, so the majority of solid fabric projects are blankets or afghans.

Despite the fact that you can do three dimensional objects (like stuffed animals) with knitting, the speed of crochet along with its strength (and no elasticity) make it better suited for these types of projects.

Then we have my favorite: Tunisian Crochet.  Since it is a hybrid of knitting and crochet, it has the strengths and weaknesses of both, and yet it has subtle differences that make it perfect for certain projects, more so than knitting and crochet.   

There are two elements of Tunisian Crochet that have ’hooked’ me: it is extremely diverse with stitching possibilities and because we use much larger hooks with it, it is much faster than knitting or crochet.   

Other little perks with Tunisian Crochet include: it uses less yarn that crochet, and only slightly more than knitting- in most instances.   The double layer of Tunisian Knit stitch makes it perfect for warm objects like hats, outer wear, blankets, shawls and scarves.

Because it is very sturdy, it would work well with structured garments, like blazers, although I haven’t found many patterns like that, yet.  

With some easy tricks, it can be as fluid and beautiful as knitting for light weight cardigans and tunic sweaters.  However, Tunisian Crochet does not have the two way elasticity of knitting, so form fitting pullovers are not the best with TC. Also, the lace made from TC is rather linear or geometric in its nature, and lacks the visually complex grace and beauty of crocheted lace.

With the internet and local gatherings, needleworkers are integrating themselves more and more.  The ‘snobbery’ of knitters is being humbled by the incredible number of projects that crocheters are able to finish for their chosen charities or gifts to their friends and family.

The overly thrifty nature of crocheters is being enlightened that working a piece of art is not a guilty luxury, but a joy of the heart.  

Slowly but surely, designers are creating patterns for crochet clothing that is just as beautiful and functional as knitted garments... and even slower, the publishers are learning to venture into undiscovered territories and print those patterns for crochet that are more artistic, and less utilitarian.  The progress is slow, but it is a definite progress towards all needlework styles being equal and enjoyed equally by all.

Dora has more on this topic at CrochetInsider.com
Jean Leinhauser ran a Poll at the  “CrochetPartners”  board, now at Yahoo.
JD in St. Louis, posted comments on her blog, and others have commented on that.
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Why is Crochet the Underdog of the Needlearts World?