You'd think it would've been quicker to upgrade, but with local, development, staging and production environments to upgrade and test, our project managers would probably schedule a week or more for the task. Furthermore, it's a large company, but currently a low-priority project that nobody wants to touch.
If we get the job to build the new site, the CMS decision would likely be down to which product our company wants to sell. These days, our agency prefers Pirobase, Drupal or Liferay.