The second difference is much more subtle and more interesting. Historically women tended to collect things for aesthetic reasons. They would collect things that are pretty or that had sentimental attachment. One of the greatest stamp collections ever assembled was by a woman who collected only blue stamps. A man would never have thought to arrange a collection in this manner.
Boys seem to collect things very systematically and are very concerned with the market value.
My sense is that this is changing. As more and more women in the last 25 to 30 years are part of the business world, they are probably starting to collect things in a systematic style and for the market value rather than only for the emotional and aesthetic value. My impression is that collecting is certainly as popular as it has ever been among adults, perhaps more popular. It seems to be less popular among children. The nature of collecting seems to have changed somewhat.