The first type is full of professional developers and publishers. This kind of conference tends to be about business, technology and innovaton. The tone is often somewhat introverted, reflecting a particular culture of game developers. It is respectful of indie games but new-fangled concepts like social games are regarded with suspicion.
The second type is the peripheral event, and attracts brand people, educators, serious games people, gamificators, students, transmedia makers and (until recently) virtual world people. Presentation tends to be about pitching companies or theories, wide-eyed and optimistic. Attendees tend to be less aware of games as an industry, and often think of game developers as inward or backward.
They don't really gel. The first group is much better at execution but consumed with conservative ideas of what it should be executing. The second is more liberal, but tends to fall back on behavioural 'games' which aren't strong. For the first, games are a medium and a culture. For the second, a tool for doing other things. The first says 'gameplay'. The second says 'engagement'. The first is overly hard-headed. The second is very flaky.
Even in big conferences like GDC the two tend to separate into distinct streams, conferences and attendees, like oil and water. As a result, both tend to talk to the same kind of crowds again and again and make the same circular arguments over and over. Is there any way to bring them together?