Why do forum posts rank higher then blog posts in serps?

[cigarette]

Hi,
Can anyone tell me why it is that forums get spidered instantly by google and rank higher then any blog posts nearly always. Is it totally due to links or is it another factor?
And why does vbulletin forums always rank highest? Is it due to design?

[lim (x³-7x²) = ∞]

threads are linked from strong pages - subforum listings, probably blogs needs more incoming links (and not only from your forum)
but we don't know for sure, because google use large amount of factors (and we don't know most of them)*

may be blogs are more clicks away from main page
may be there is no problems with blogs, just needs time

google will not rank sites by used scripts, it always separate Content from Interface, most likely design doesn't matter much
to answer your question "why" - probably your searches was in niches where vbulletin is more popular (vbulletin powered forums have more relevant content for you)

*from latest news - google hints us that they may give priorty to sites wich loads faster