The documentation for WampServer is minimal at best. There's no installation walkthrough, save for what you get when you run the installer itself. There isn't even a good explanation of the various functions available through the tray control app. I had to figure out on my own what the "online/offline" function was for. I also ran into port-conflict issues, but there is at least a test function within the tray app to let you know if port 80 is already in use. It's not nearly as detailed as the port-assignment tool in XAMPP, but it does at least help you figure out what might be blocking vital ports.
Recommended for: Those doing PHP programming, especially if you need PHP debugging tools as part of the stack.
WampServer's control panel provides quick links to configuring many of the components in the stack.
XAMPP 1.7.7 (1.8 beta) XAMPP, from Apache Friends, is one of the best-known and consistently maintained development stacks out there, available not only for Windows but for Mac OS X, Linux, and Solaris. It includes Apache, MySQL, PHP, Perl, and a few other bits of plumbing such as an FTP server and a mail agent, should you need them.
XAMPP comes in two basic incarnations: with and without an installer. The "installed" version sets up XAMPP as if it were an application, with the program icon launching XAMPP's system-tray control panel app. The installer-free version is just an archive that you can unpack anywhere, but which needs to be configured manually by way of a batch file. You can actually skip the configuration step if you've unpacked the whole of XAMPP into the root directory of a device (for example, a USB flash drive).
Certain components of XAMPP -- Apache, MySQL, and the FileZilla FTP server -- can be run either as a standard Windows application in the background or as a system service. The former is useful if you want XAMPP to run with a minimal system footprint and if you hate having unneeded system services hanging around in the background even when they're not being used. XAMPP's version of Apache also comes preconfigured with SSL, which is handy if you want to test apps that need it.
XAMPP's system-tray launcher lets you control the activation of each major component of the stack, and install or remove Windows-service versions of each stack component where available. It also provides you with quick access to the management consoles (Web-based or otherwise) for each component, and a minimal event log for the whole stack.
One problem I immediately ran into: When you launch XAMPP, you aren't warned if any of the running services conflict with existing port assignments. My copy of Skype used port 80, which resulted in Apache refusing to start -- I had to debug it manually.