Well in some ways it harkens back to the Novel vs. Short Story concept. In the short Story you have to learn the crucial elements and have closure in a relatively short amount of time. It is a totally different writing style. Some folks are better at one medium or the other. I think though that this theme is very pertinent to RPG play today.
1. People have shorter attention spans and despite advances in tech, less free time in many cases. So a short campaign may work better.
2. The old long deep campaign was the old Way in many cases and I think it is inevitable that evolution will take us towards shorter campaign games.
Remember too, Poker, Monopoly, and such games are the same game every time even though its always a new game. Giving players a plethora of choices is what will ensure replayability.
Sean