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First of all, XOOPS is CMS/Portal, and Wordpress is mostly blogging platform. It's enough if you want to focus only on content making (only articles).
On the other side, XOOPS is CMS/portal, that means that with it you have better modularity.
You can integrate Worpress in XOOPS (Xpress module), but you can do lot more. Download it and install it in local.
Xoops lacks good comment system and SEF urls (different from module to module).