Just to be clear, here at NetAdvisor we love Drupal but we also work a lot with WordPress. Ultimately it really depends on what the customer wants, and what type of website they need. But for your interest and research, have a look at this great article to determine the True Cost of an Open Source CMS:
On Saturday March 11, 2017 (approximately 8am) there was a massive power loss at the Vancouver Data Centre where NetAdvisor web, email and database servers are hosted. Due to a perfect storm of technical failures, servers were abruptly crashed without properly shutting down, and resulted in lengthy downtime while services were being restored, disks were being scanned and databases were being recovered.