I'd also like to take a stab at the PPSC hating, perhaps because I was the one who set up that game. PPSC is only a perverse incentive if you want it to be. Most players understand the difference between a defeat and a draw, and even in PPSC you're probably going to get more points by arranging a draw than you would stealing one or two more centers before another player solos. There are exceptions, but they are few.
I've heard a lot of people say WTA is truer to the intent of the game, and they may be right. Diplomacy is ultimately about working together to achieve success. WTA theoretically takes all the incentive out of SC stealing in the face of a solo, because you won't get any Dip points out of any of those extra centers if someone else wins the game outright. Better to put your best effort into a draw. But even WTA doesn't always stop a player from doing some stupid SC stealing. Take this WTA game (http://webdiplomacy.net/board.php?
gameID=74726), where in Autumn 1912 Turkey forgoes a chance to force a draw so he can go grab a few more supply centers for himself. The result is a German solo.
There is also the case in WTA of nearly defeated players agreeing to help another person solo in exchange for a guaranteed survival. One might rather have a "survive" on their record and let someone else win than play for a draw they won't have any part in.
This is really what PPSC is for. A player can get some satisfaction (and Dip points) out of surviving a game even if another player wins. In the case of newer players (where your Dip points are scarce and surviving is sometimes the best you can do against tough competition), the PPSC set-up makes a lot of sense.
Ultimately a player's behavior is going to be determined by what they're in the game to do and what the circumstances have been presented, regardless of WTA or PPSC settings. Some players only want to win or die trying. Others will fight to ensure a draw. Still Others don't care what happens if they can pay back the guy who stabbed them. And still others just want to paint as much of the map yellow as possible so they can look at it later and think it's pretty.