Tell me the main difference in real time scenario..?

Not sure if I fully understand the question.

So running a application under window services is control by window services.

If wTM can be run under window services you just use window to start the services.

wTM can by hosted in IIS as well but you must choose one or the other.

If wTM is hosted in IIS you need to figure you apps pool for wTM memory pool to be run within it's memory pool and you need to add wTM site to IIS.

Real world, most prefer to use wTM running under IIS because you can capture more data and log if something is wrong. IIS is control by MS and we can capture more data if something happen.

If wTM is hosted as a window services and something happen, we don't have a good way of capture log. window services can be set to restart the services if something happen.

Did you mean Real World? It's really just a matter of preference. If you are using tmweb and not running datacap navigator you may want to run wTM under IIS. You may prefer this option to save resources. For instance, when running a virtual machine on a development workstation. In a shared environment you may wish to use Navigator and leverage LDAP user repositories under WebSphere. One advantage of using Datacap Navigator is load balancing. If you intend to use secure sockets some additional maintenance is needed if you want to use HTTPS with both WebSphere and IIS rather than one or the other. When running as an IIS service, it can be occasionally overlooked when the team bringing the services up after a patch/maintenance window are the platform rather than application teams. Windows Services tend to be more "set and forget" when configured for automatic startup and easier to monitor.