They are phpBB, vbulletin and Simple Machines forum.
The only reason I cant choose is because I would prefer free But also would rather pay if it is going to be better.
I kept finding posts about duplicate content penalties when using SMF.
I the read that phpBB can be tricky to mod, ie the SEO mods they put out. I am not horrible at techie stuff, but would rather steer away from that kinda thing (unless it is easier than it sounds).
And then vbulletin, which is what the warrior forum uses, it costs $180,and then the SEO application is $150. That is a big investment for me, BUT if you think it is the best choice then I will "save up" and get it.
Would like to hear what you use, some threads (on other forums) claimed that SEO optimization for forums wasnt needed anymore as google is more advanced now. I dont know.
PS, is a forum best put as subdomain like: forum.mainsite dot com
or mainsite dot com/forum?