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Take you time choosing though, as it is an important decision and one that is different for each user depending on their technical aptitude and what they are wanting to achieve. The last thing you want is to chose your CMS only to find 6 month down the line after you've put in hundreds of hours into content creation that it isn't going to be able to do everything you want.
I used to solely use Xoops, but now I primarily use Drupal. My reasons for switching were more technical (including SEO) than usability, but that was my choice and everyones will be different. Have a read of
this article I wrote on why I switched from XOOPS to Drupal. No CMS is perfect, so it is a matter of finding the one that suits your needs now and making a best guess on which CMS is going to evolve in a way that suits you.