I think a lot of the larger Yorkies come about because breeding the big bitches is safer and creates larger litters for sale. There may be a premium paid for the smaller, show quality dogs, but the breeders of larger dogs make it up in volume and safety for the birthing females.
Unless you are planning to show...what does it matter? They're all great and have the fabulous Yorkie temperament and look. I don't even care about breed purity...I now have a Chorkie and she's one of the most wonderful pooches I've ever known.
