Most of the applications that you can build on one platform could be built on any of them. Sometimes, there is a specific reason to use one platform over another. For example, if you are just setting up a blog and nothing else, you should use WordPress. Or if you need the features built into a specific distribution of Drupal, like CiviCRM, your choice should be clear.
However, if you are not a developer and need something new built from scratch, it is much better to find a developer you like and trust, then let them select a platform based on their comfort level and the needs of the specific project.