9
Sure - try it out, but even though phpnuke is more known and has a shitload more modules, it is also harder to setup and not as good as XOOPS (my personal opinion)
I could also recommend that you look at
mambo (www.mamboserver.com)
drupal (www.drupal.org) and
e107 (www.e107.org)
Download them, unpack them, upload them, read the install instructions and try them out. Whether XOOPS is the best for you depends on how intuitive each CMS is to you and what you need it for.