@JECE - I know you have had substantive response on webDip, because I was one of the people who responded to you. You just have a tendency to dismiss the opinions of everyone who argues with you on the subject.
Anyway...
There are two main reasons to dislike PPSC. The first is the one that's oft-debated, but it's not the reason PPSC is bad. It boils down to:
REASON #1 - PPSC IS BAD BECAUSE WTA IS RIGHT
Essentially, games should be Winner-Takes-All because that's the way it was written in the rulebook, and we should stay true to the rulebook. In competitive Standard play, I definitely agree with this - the standard board is specifically designed around this being the case - but in a more casual setting I don't think there's a massive problem with having a non-WTA setting, especially considering the imbalance present in many of the variants here.
A huge problem with PPSC debates is that both sides assume that's the crux of the issue, and because it's something of an ideological difference neither side will ever be convinced by the arguments of the other. I've tried to raise other reasons in threads about PPSC on webdip, and they're always completely ignored by everyone while they continually talk about the above point.
The real reason to dislike PPSC is:
REASON #2 - PPSC MAKES NO SENSE AS A NON-WTA SYSTEM
Let's assume that we're okay with non-WTA scoring systems. We're looking for a system that specifically encourages you to go for Supply Centers, and we want it to reward you based on the number of centers you achieve.
Would we ever choose PPSC as that scoring system? The answer is no. PPSC doesn't reward players based on center count in all cases - specifically, it splits the pot equally in draws - and that's a massive problem, because it completely screws up the objectives. For players with few centers, a draw will award them with more points than a survival to a solo would, and for players with high center-counts, a survival to a solo awards them more points than a draw.
This means that instead of the aim for all players being to gain centers, which is the idea behind the system, the aim for large players becomes 'force someone to solo' and the aim for small players becomes 'stop anyone from soloing'.
Of course, the large players, being large, have much more strength and are easily able to force *someone* to solo. However, this someone often isn't them, which results in a conflict of interest - they're supposed to be playing to maximise their SC count, but they often need to maximise someone else's SC count to ensure the PPSC scoring, which means less SCs for them.
C-Diplo would solve this issue. C-Diplo is what PPSC should have been from the start - regardless of how the game ends, the points are distributed according to center-count. This means players are always playing to maximise their own center count, instead of having to throw the solo to someone else to attain that result.