I'd go with vBulletin on this one, probably because I find it easier to change things and such.

I haven't ever been on the admin or mod side of vBulletin, just the user side, so maybe that is why I don't take to it like so many others do.

I think vbulletin is the best because it is very user friendly and it packs alot of features that are definity worth the cost to buy it.

I love vBulletin. It is so easy to use, plus the look is so clean and professional. It is the greatest forum software by far!

I would like to code my own forum system when I have time. I am actually trying to get into planning stages for that now.

However, I do like vBulletin the best. (I have been on the vBulletin boat since the early 3.0.0 releases, so I am unfairly biased).

Actually building your own forum software is not that hard. It's whether you plan on releasing this you have to worry about ease of use on the Admin side. Also if you plan on selling it or letting others use it you have to be able to support it.

funny thing, my VB license expired yesterday. the most funny thing was that I never used it (maybe, 1-2 months?). smf is way more stable and has way more capabilities than most forums.

mybb is nice too, but not that many themes available which is a downput. phpbb is a plain security exploit waiting to happen.

Well, even though there are not too many themes for mybb, that to me isn't that much of an issue, as you can easily make a custom theme...

I didn't like the theming system of SMF, at least when I tried it, you had to edit all kinds of files, and it seemed to me it didn't work too well, and an upgrade to the forum software, completely messed up the theme.

phpBB has a simple, user-friendly interface, a helpful FAQ and a generous administrator control panel.
You can choose the databases server (MySQL, MS-SQL, PostgreSQL or Access/ODBC), the functionalities (at first I was a little discouraged by the mods installation process but I found great support on the online community and the documentation they provide answered all my questions) the skins... Everything is customizable so you can create the forum you wish.

If you haven't got much time, and want to see what the new phpbb3 can offer, just try it out on this host : create forum

Hope this can help!

I'd have to go with vBulletin.