 Good Question
Size does matter to a lot of people, breeders included. Most people have a preconceived notion of what they want their new puppy to look like. This is often formed by a Yorkie they have seen on TV or belonging to a friend. Since there are different sizes available they are just shopping for what they "think" they want. What they actually want may change dramatically with a little education. I haven't personally had any health problems with the smaller ones, they are definitely more delicate but not predictably unhealthy. I personally think the five to six lb range offers the most beautiful specimen, making the elegance and graceful movement evident and offering enough leg to show the coat.
Many of the puppies pictured in the teacup will be larger yorkies, you can see the evidence of this when the breeder doesn't update pictures as the puppy grows. |