I agree that the typical 360 owner is different from your typical Wii owner. 360 owners may still end up buying more games in the long run, but I disagree with you when you say the Wii is a fad. Microsoft must think it's more than a fad if they are trying to copy the idea of the Wiimote controller.
I also disagree that the Wii is selling because it is $250. People have been paying $400+ for one on Ebay for more than a year. If price was the only reason for the Wiis success, so many people would not be willing to pay as much (if not more) than a 360 for one.
Neither of us can prove our opinions as facts. No one really know for sure why people are buying one console vs. the other, or what use they get after they've been bought. We can go by what we read on the 'net and what our circle of friends say. I have yet to see any wide ranging survey that would give us some definitive reasons for the sales. I can see the reasons for your points, and I hope you can see mine. It really doesn't matter in the scheme of things anyways. I'm happy with my gaming setup, and I'm sure you're happy with yours. It's just good that we have options, at least when it comes to consoles. Sports gaming options are becoming increasingly limited, and I think that worries all of us.