5
One big difference between the current version of Xoops, and earlier versions of XOOPS (like the one exoops is based on) is that for the current version, the developers made an exhaustive effort to reduce the number of SQL queries used to create a page.
Add to that, the current version of XOOPS uses a template cache system (Smarty) that further improves performance (if you turn it on) since it caches the results of the php and MySQL when a page is made, and doesn't need to pull on the database each time a new user requests the same material.
Between the two items, it's a huge benefit to performance.
I came to XOOPS based on it having the best performance I saw in the CMS I compared (and that was early, before exoops even existed... even then XOOPS was well coded for great performance). XOOPS has only improved since then, which shows the developers keep the right priorities and avoid the bloat that happens with so many projects.
But, some other pluses of XOOPS are the helpful community here and the ease of using XOOPS itself.
Plus, you've got to credit the developers for releasing solid code time after time.
Maybe exoops has something I don't know about to match this, but, I'm not aware of it.