What is the difference between difference between installing XAMPP as a service or as a standalone program
I guess you mean to install a server like Apache or MySQL as service, and not XAMPP.
- A service can run without a logged on user.
- A service runs in it's own security context and environment, and not in the same as the current logged on user (if any is logged on).
- You can manage services (start/stop/status/logs) through the network with the Windows management console.
Well, XAMPP is a development environment, so it should be enough to start the servers as programs when you need them (while you are working on your html/script files).