best open source bb software?

I'm looking to set up a forum, so what would you say is the best open source forum software around? I know of PhpBB and SMF, and I've heard of a few others; UltimaBB, PunBB, but other than that I don't know much. I've thought about going with anonymous image and text boards; in that case Wakaba and Kareha, but I'm leaning towards traditional forums.

So what should I go with?

Thanks.

SMF is fucking fail. Why can't one of these board developers make a BB system without a default style based on spacer gifs, font tags and aids? I believe PunBB is one of the only boards to have figured this out, and thus it deserves respect.

Also, what's wrong about lacking PMs, file attachments, polls and unnecessary javascript shit in the post form? The only thing that might suck is lack of subforums on a big site but I doubt you're founding the successor to Somethingawful forums or Gaia based on advice of 4chan.