Last week I did some comparative study about various forum based tools available. We also taken hosted forum services like Hoop.la!, but we decide to host our own forum since the user base is large for our site. Eventually we shortlisted the following tools.
Though most of the feature been supported by all the tools, It is disappointed that JForum is not supporting SEO URLs. We need our custom implementation to do it. Though they revamp their architecture on coming release (JForum 3.0), which is currently on beta. There is no definite statement about it’s production ready. Bot vBulletion and PHPBB3 supports SEO urls by modules we you need to plug in. It won’t support by default.
SSO feature is not covered in the diagram where JForum support with custom module. You need to extract their SSO class and override it. PHPBB3 does have session sharing support, but not having SSO option. vBulletion has it in build.
If you are a java expert and don’t like to code with PHP go with JForum, though you will need fair bit of customization.There is nothing much feature support difference from vBulletion and PHPBB3. If you willing to spend around $199 go for vBulletion but you can’t customize as you like. Best fit in that case obviously PHPBB3.