I have never had a problem with phpbb. Just because it is free does not mean it's not good. However I plan to upgrade to Vbulletin if I see my forum really growing. But go for owned. It's a better investment.
I suggest getting a leased licence for the first couple of months to see how things work out. There's always a possibility that you decide to can the project or it just doesn't work out. The first month or two are crucial to getting really "into" managing a project, so a leased licence should be better in that "test" period. You can always buy a owned licence when you're sure you're going to need it...
Leased is no updates or any of that and you have to pay each year. Owned is updates for a year and then if you pay 30 a year after the first year, you get updates for each additional year.
The smart way to go is to get an owned vBulletin license instead of a leased one. An owned license is permanent and doesn't cost much, but a leased license expires, and once it expires you'll have to pay for it again or upgrade to owned. You will save yourself time and money if you just purchase an owned license.