Nancy, an important point is to judge for yourself whether something is "quality". Just like any other item, you will come across sellers of paperweights who describe them as "superb", "top quality", "stunning", "never seen anything like it before", etc. etc. etc. Don't believe a word of it until you have checked it for yourself.
But just like everything else, until you have seen the really stunning items, you will only have lesser quality examples to judge by. And browsing books and websites will only give an impression of what quality a weight may have. It's only when you see it close up in reality that you can make a true judgement. And even then your own personality and perceptions will have their effect.
Personally, I'd rather have a well made Paul Ysart millefiori weight than a Stankard floral item, even though the Stankard piece usually will, with its true-to-life flameworked flower, and its pristine dome clarity, have a much higher quality of workmanship and visual wonder than any Ysart weight.