I could go either way.
Personally though I think there is to much of an emphisis placed on campaign based play.
I know that if I'm running a game for a bunch of new players I use the one shot model first. It allows for error and it gives players room to learn.
I find that sometimes campaigns lead to people being too protective of thier characters and, more annoying for me, the DM's being protective of the player characters. When I read posts where DM's say things like " I couldnt kill off that PC's it would throw off the campaign" I want to just scream. I acknowledge it's a difference in playstyle but it still grates on my nerves and feels as artifical as hell.
With one-shots you dont have that problem. If they die, they die. Time to roll up another character or use another available pre-gen. Done? Okay let's play!
That said there is something to be said for playing in a long term campaign, but not a whole lot because honestly for me, the stuff that happens in a long term game is a lot cooler when it's actually happening than when I try to tell the story of what happend to someone else. Most of the time those campaign stories, unless they are recorded and made into story hours, are a serious case of the you-had-to-be-theres...