And second, doesn't each approach (even if you prefer it) have pitfalls? What are they? How do you deal with them?
Absolutely true! Of course, I am brawling here, so I cleverly omitted the bad points of my preferred style. But since you asked, I'll admit them.
And the big one is the one you say: the longterm campaign is indeed a pitfall for the unhappy player. If you don't fit into the group, the long term campaign is your gaming death sentence!
but I suspect your'e just a bit wrong:
E.g. all else being equal, I posit that the unhappy player can be a bigger problem for longterm play, because if you want to change something as a player, you actually have to discuss it. Whereas in short-term play, the "gaming contract" is reset after a few sessions--and at that point, it's easier to drop out, propose a different game, or look for a chance to GM (so you can demonstrate how you like games to be run).
You have entered the realm of the griefer!
The griefer is the unhappy player who doesn't fit in, and thinks everyone else is doing it wrong, no matter what the other group's enjoyment level is. He often likes to sabotage other people's gaming, because he is at heart, a selfish piece of crap.
I would characterize most forgies as griefers. This is (obviously) based on my completely unfair bias against them, but also because of anecdotal evidence. There's a profile, and many of them do fit. They can admit it or not.
So unhappy gamer: he's in the game that everyone else loves and he can't stand. Sound familiar?
Ok, pretend he's a normal guy.
I think it's more likely for an unhappy "normal guy" player to completely drop out of an otherwise functional group. Normal guy goes on and forms another group or joins another group. Bam, he's still in. Or maybe he finds out he can't be happy anywhere and quits gaming altogether. Whatever. The guy is meaningless at that point. For some people, gaming is just a phase, anyhow. Oh yeah, I totally did this in February 2006. I got to the point where I was unhappy driving 30 minutes to the game and not getting much sorcerery and trickery in. The GM made some rules mistakes I thought were kinda boneheaded and questionable. But I didn't try to ruin the game. I quietly put out feelers for new players and an alternate game night. I still keep in touch with the old group. I even have a player that straddles both groups. See? No prob. Because I'm a
regular joe and I have no interest in ruining anyone else's good time even if my experience wasn't "perfect".
Nor do I feel traumatized or psychologically damaged by my experience.Also, of note, I didn't wait until the end of campaign to drop out. I wrote a nice email, made my friendly excuses for leaving, and offered guaranteed slots to anyone who really wanted to play in my campaign on the alternate night. I think I made it clear I wasn't trying to steal players (and I truthfully wasn't). I didn't expect anyone to want to play in two games a week, but I was surprised when one of the players joined my group (and stayed in the old group) anyhow.
But the griefer! The griefer doesn't play that way.
The griefer sticks around and starts trying to convert the group or sabotage it. His good time is the most important. He's the quintessential (dare I say it? haha) date rape advocate. He starts screwing with other players, or screwing with the group's ability to accomplish .. whatever it is that the rest of the group is trying to accomplish. He's looking for PC vs PC conflicts all the time. He demands his "fun" even if he has to take advantage of other people in the process.