CMS and learning curve.
If you are looking for a CMS, the "best" one will be the one that already does, or can be made to do exactly what you want. The pickier you are, the closer you might come to needing to learn how to use your chosen CMS's more advanced features, or a custom CMS built for your own needs. That takes either time to learn to do it yourself, or the money to pay someone else to do it for you.
In my own personal opinion. Joomla is the best cookie cutter site maker out of the box, with plenty of easy to use add ons to choose from. If you need a more customized setup, you might take the dive into learning to use TYPO3, though the learning curve is higher, it can do amazing things! I have heard good things about Drupal, but have not used it extensively. It might actually be a good middle ground to check into.