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Forum Moderators: ergophobe
Really your only option is to install all three and experiment, and then you can choose the one which seems the easiest and most adaptable for you.
Blog in Joomla is not upto the mark. You can have a bridge to Wordpress however quite tricky. Forum component is quite good.
You may also bridges between the wordpress and other popular forum scripts such as SMF/Vbulletin.
All the best