Forum systems

[Logseman]

While I'm young in age, I'm fairly seasoned with forums already, and now I'm going to host one along a bunch of friends. We're aiming high, our topic is not well-covered like it used to be and I think we can become the reference forum for the matter (Spanish politics, if anyone cares about it).

I've seen that vBulletin is the forum system of choice by Mobileread and other big communities. However, I've come to know the cost of the vBulletin suite and it is too high for our budget, about 300 dollars for the whole thing, though I know it is really powerful. In the other hand, we have PhpBB, an open-source, free forum system which is pretty much the standard thing among the web. I know of the existence of other forum systems like SMF or Invision Board, but I can't say anything about them as the forums I visit use usually one of the aforementioned flavors (vB or PhpBB).

However, now that I'm paying the hosting costs (I got a good deal on that, thankfully), there comes the time for serious business. Since you're used to forums and some of you have probably hung around forums before I got out of my diapers, I appeal to your experience. What is your experience with Forum Systems? What would you suggest for a forum which has spawned a blog and some presence in social networks?

Thanks in advance.