There were definitely a lot more of the younger/newer owners at DW. That said, DCS still does pretty well, doesn't it? I think people are willing to spend the money on a big show when it's a known quantity, but after 17 years off, DOA was basically starting fresh and a lot of people weren't clear on what they were getting for their fees. That, combined with the Expo's proximity to another established event in the same area that had been announced quite a while beforehand, was a big factor in the different levels of turnout, I suspect. (I know Rob R has said that they were always intended to be very different events but I don't think a lot of people saw it that way, especially when the Expo was going to do some of the same driving tours that were already planned for DW.)
The next Expo AFAIK will be in a different area so the question of one event vs. the other should be a moot point, but I agree that there should be more collaboration between DOA and local clubs if the next one is held in an area where there's already an active group. DeLorean ownership and appreciation shouldn't be a competition and I think we can all learn and benefit from each other's experiences.