In the past, a tobiano was not as desired because of the tendency to have so much white. And you are correct, there were not as many of great quality, as there were of the overo patterned horses. Since many QHs carry some type of overo gene, although recessive and not expressed, the best quality paints began to emerge as "crop outs" from the best quality QH stock. As we have continued to breed, we have developed better and better quality. You will definitely now find some modern day tobianos that are fabulous as well. There are even a few very nice homozygous tobis, which is far more rare to find quality in. Even today, though, you will find that many breeders/exhibitors/judges prefer the minimal white overo in the show pen, to the loudly expressed overo or tobiano. This is even more true now that we are able to dbl register some paints as QHs.