If I was to create a server right now, I would most likely use either xenForo or IPB, mainly because I own a license for both. Using a free forum software that you don't have dedicated support team for just doesn't seem like a good idea if you have these other options. If I did not own a license for a paid forum software, I would most likely use MyBB.
Paid softwares also have constant updates to them, while free softwares are updated much slower, in most cases at least. I love seeing the software evolve and gain new features, which you really don't see that much in free ones.