what is the best forum software

[Vanilla]

Well, from what I've experienced, MyBB tends to be the best and fastest (in tests) if you're going to have a normal sized forum.
- Seems like other people also have this experience: http://www.theadminzone.com/forums/showt...hp?t=42840

But if you're going to have a large (100.000+ Active users), then you might wanna check out either VB (Paid) or PHPBB (free).
From what I've experienced, they seem to be able to handle immense overload better than MyBB. But such overload only happens in extreme cases anyway, so in other words, I would recommend MyBB.

Get MyBB here: http://www.mybb.com/