Only one vote for MyBB? I use both phpBB and MyBB in the past before. However, i feel that MyBB is better than phpBB. Although MyBB have lesser ''powerful'' plugin than phpBB but it have easy to control ACP.
My favourite forum software overall has been phpBB for a while now. I do like vBulletin's features and it definitely can do things phpBB can't but I am not rich and I cannot afford expensive software for a website that does not have a lot of traffic yet. It becomes justifiable when your site becomes profitable.
I would have to go with vBulletin. I've never hosted my own forum, but I generally prefer it for use because it's so familiar to me. One of my most well-loved forums that I was a member of for a long time used vBulletin before they got too popular, so I got used to it and I really enjoyed the ease of use. Now that I belong to tons of different forums and message boards, I still prefer it because it's so familiar to me.