Dear Paperchicken,
First of all, there is no basis of comparison whether YPAP forum is
better or SGforum better.
But in YPAP forum, I get more kick, due to some "hotting up" effect
and changing to confrontational mode.
I wasn't serious
when I apply to join YPAP forum but to test on PAP's "Open,
Inclusive" concpet. I made known to them I am from Workers' Party.
Well, it takes a while for my account to be activated but at least,
it got activated. 
There are some good forumites in YPAP forum, people like StrayCat
(insightful and creative), Lai (knowledgable in infrastructure
development due to his profession and also he is pretty good in
Singapore political history), Vincent (sharp and very logical
thinking) and even Modeus has his pluses. Of course, there PAP
"bouncers" around, like Elfred. It is a good training ground for
people like me. I need sparring partners as well as dancing
partners to shape me up.
AS for SgForum, I think there are more "silent readers" around,
some are critics of both PAP and opposition. But the fact is, it is
a citizen's right to make his political stand and I believe, one
has to make his stand. I do not believe in the "perfect" system,
but I do believe we are far behind time in political reforms. There
are really much to be done to improve our society as a whole. I
believe there are also PAP bouncers around and they are more
"dangerous" than Elfred in YPAP. They are just waiting to bite
hard, I guess.
It may seem to many
that YPAP is a "hotter" place, but to me, SgForum is a more
dangerous place. 
As for why WP doesn't have a public forum like Sgforum or YPAP, you
must read carefully the political act which restrict internet
public forums which requires them to "register" and forum hosts are
liable for all sorts of charges and responsibilities. Sintercom
closed down basically of that. To me, since only YPAP forum
ultimately become the only political entity that could host
internet political public forum, just make use of it lor! 
But WP does have created a "closed", invite only, internet
political forum under Yahoo. It is not open to public for the most
obvious reasons.
Goh Meng Seng