Skiing/boarding videos are better in my eyes for one reason: Skiing has a season. Theres a limited time for filmakers to get thier shots and produce the movie, and all ski movies tend to come out around the same time of year. This creates fierce competition between these companies, and producers know they have to be the best out of the 10 movies being released. It causes them to strive to make the best possible to attract the audience.
In skating however, there is no season, and skate video's come out whenever. Thus, as long as you release yours, no matter how good it is, it will probably get bought if its the newest thing out. Thus, the quality doesnt have to be so good, because you arent competing.
I guess its like natural selection when you think about it, kinda funny.