Virtual Server multiple service ports

You can configure one virtual server for all ports but that creates a security vulnerability. Its better to have a virtual server for each application service port you need - that way you are limiting your network exposure to just those known ports.

The other advantage to having multiple virtual servers for each port is it allows you to have better insight as to the health and availability of your application. You will know if a particular component is down or not (HTTPS is up on the web server but the app server is down for instance).

Lastly, each virtual server will have corresponding profiles that can help in logging events. If you're using AVR (which I hope you are) or at least request logging then you can see each transaction as it transverses both the F5 and your application.