Here is the Great Dane Club of America standard...I don't know about Danes per say but I know that with my Pyrs shorter is better...Less wear & tear on the ol' hips & joints...I'd much rather have a shorter dog than a dog with hip & joint issues!
http://www.gdca.org/standard.htm& check this link down through the size section:
http://www.faqs.org/faqs/dogs-faq/breeds/greatdanes/ Size
The AKC OFFICIAL STANDARD FOR THE GREAT DANE states: "The male shall
not be less than 30 inches at the shoulders, but it is preferable that
he be 32 inches or more, providing he is well proportioned to his
height. The female shall not be less than 28 inches at the shoulders,
but it is preferable that she be 30 inches or more, providing she is
well proportioned to her height." It is common for males to stand
about 35 inches at the shoulder, and to weigh about 150 pounds.
Females are commonly about 32 inches tall, and weigh about 120 pounds.
Puppy buyers should remember that "bigger", is not necessarily
"better".
Thesize has nothing to do with good or bad breeding(unless they are WAY out of standard) but more so personal preference of the breeder or perhaps just what sells best.