Why use ExpressionEngine?

We use EE over over content management systems for two big reasons: Security and Extensibility. On the security side, we have had a number of clients who come to us with their CMSs being hacked to bits, especially on the WordPress side. EE has taken a number of steps to ensure they have all security holes plugged, and limit the amount of holes a user can purposefully leave (i.e. using weak passwords). The extensibility of EE is the other thing. With the introduction of the CLI tools in V6, getting new add-ons up and running becomes a breeze. If the add-on doesn't exist, building it becomes simple and straightforward. We have sites that get a few hundred thousand hits per month and have advanced user features, all of which would be a lot more troublesome to implement in other CMSs (and we've tried).