1. WordPress is Easy
Once you get the hang of it WordPress is a beautifully intuitive system to operate. Ok, some things are a little tricky but they're a lot less so with WP than any and all of it's rivals. The complication comes from it's power, but for most functions it's wonderfully intuitive.
2. It's the Biggest and Most Popular CMS in the World
WordPress is the most popular Content Management System (CMS) in the world, which means more people run it, innovate with it and improve it than most of the leading rival systems put together. That scale of use means it evolves and improves faster than all the others.
3. Over 17,000 Ways to Enhance Your Site for Free
Plugins for WordPress are like apps for your smartphone; they massively increase the functionality and possibilities for your website. The vast majority are free and there are more developers creating new plugins or updates to plugins than any other system. This includes shopping carts, photo galleries, currency converters, Google Maps and thousands of other very handy functions to beef up your site and help your visitors do more.
4. Themes - Get a Highly Professional Look for under $100
Because the content is always kept separate from the design, you can simply switch between layouts and designs in seconds. Over 1,400 themes are free but from about $25 to $75 you can get professionally designed themes which would cost $1000s to have done just for you. They're all hugely customisable so you don't have to worry about too many websites looking the same.
5. WordPress is Free
Unlike so many dreadful push button, turn key website solutions, the WordPress.org system is open source and completely free.