WordPress vs vBulletin
It will be like comparing apples with oranges as one is a Blog Script and other is Forum. But both the scripts are based on similar technologies ( php/mysql) and there are some similar features.
WordPress’ look and feel is more in liaison with 2008/2009 technologies, vbulletin comparably looks outdated.
The installation, up-gradation, out of the box ‘SEO’, performance, adding plugins , changing skins and overall look and feel is much better in wordpress, pity wordpress doesn’t have a forum solution.