Bracing myself for the downvotes but meh, let's live life dangerously.
WordPress.
Why? Incredibly easy to dev against. Powerful API built in. User model. Flexible theming. Plugins for extensibility. Multisite for more complex apps.
I've built a few web apps in house using it and am now making a couple for production use. I might one day find I need to get this made bespoke but I can't see a requirement any day soon. WP does everything I need.
WordPress.
Why? Incredibly easy to dev against. Powerful API built in. User model. Flexible theming. Plugins for extensibility. Multisite for more complex apps.
I've built a few web apps in house using it and am now making a couple for production use. I might one day find I need to get this made bespoke but I can't see a requirement any day soon. WP does everything I need.