Webserver turns your computer into a ready-to-use personal web hosting server. You can host whatever you want directly on your computer and share it on internet like any website. Your computer acts like a web hosting service and allows you to make your website / application / demo accessible via internet. The server is fully configurable, modular and easy to update and extend.
Update and expend your hosting server with modules and components.
Webserver is a personal web hosting service. You can host your websites, files, applications on your computer and make them accessible from internet. You can tune your servers as you like and then host your websites, share your applications or demo permanently or for a short period of time (useful for sharing with friends, developers or clients). Develop with Devserver and host / share with Webserver.
Components : http server with Apache (or Nginx - soon), database server with MySQL (or PostgreSQL, MongoDB - soon), PHP (and Python, Ruby - soon), database management with PhpMyAdmin, FTP server with Filezilla (soon), mail server with hMailServer (soon)...
So why choosing VC9 ?
For compatibilty reasons. Usually, the Visual C++ Redistributable is already installed (this install needs admin privileges).
Why VC9 versions won't include PHP 5.5.x ?
PHP 5.4 is the last series to support Windows XP and Windows 2003. The PHP Team will not provide binary packages for these Windows versions after PHP 5.4.