[NiLuJe]

I simply tend to prefer threads for canonical, centralized documentation, especially when it concerns stuff I have intimate knowledge of (i.e., when I wrote the code).

That leaves the wiki for more open-ended stuff, or more fluid stuff that might evolve with time. Also, the forum makes it easier to react to feedback, much more so than setting a watch on the discussion page of a wiki page. Plus, no random edits from that one guy who didn't read the instructions carefully enough, but managed to make it work in a completely random way but still decided it was worth making it known to the world, effectively rendering the whole thing 33% less readable and 66% more wrong for no good reason ;p