Well I have earned the title of phpBB of the Year 2006 for a forum of mine and I might be biased
I work with all the big 5 scripts (phpBB, myBB, SMF, VB and IPB) since I'm also a forum theme designer and I wanted to have them all in my portfolio. SMF is a very good script out of the box, but I had some issues with skinning it. So far, the easiest to skin is phpBB. But you might be the kind of admin who doesn't know/ doesn't want to install many features and that would make phpBB not a good idea. Out of the box the script is very poor, but you can do wonders with it since there are hundreds of hacks that add up a lot of features.
As far as the paying options are concerned, VB and IPB are the leaders. IPB is easier to skin (access to an CSS page that makes skinning easier), but VB is cheaper I assume. You'll have to test both and see which one is better.
MyBB would be a decent free script with a lot of features VB has, but the problem is that the hacks are few. The development community is very small still and that would mean you have to wait if you want a certain feature.
I would recommend you to play a bit with them all.
As I said I use all 5 of them and cannot settle for the best one yet. I have skinning to do: that means I like phpBB more, then IPB, VB, myBB and SMF in this order. I want free, then VB and IPB are out of the question. I want many feautures out of the box: that means phpBB is out. They all have pluses and minuses and it's all about you in the end.
That's why I usually say that "there's not a bad script, only bad admins". I was able to achieve excellent results with any of the scripts in the end.
Should you need more info,please let me know.
