first may I suggest that you move this thread to the PowerCenter forum; the Platform forum is not the best suitable one for PowerCenter related questions.
Second deployment groups are one way to deploy a workflow from one system to another one, but not the only one. You can also use "simple" XML export and import; you export the workflow including all dependent objects on server A using "pmrep ObjectExport", then you copy over the XML file to server B, create / edit a so-called Import Control file (a special XML file, steps and examples can be found in the Command Reference guide, part of the Informatica Platform documentation set), and invoke "pmrep ObjectImport" on server B.
Personally I prefer XML export and import over deployment groups, but more for "historic reasons" (XML export and import works ever since PowerCenter 5, deployment groups have been invented later) than for actual experience. The only two things I can say are:
1. controlling deployment groups from the command line is indeed harder to do than XML export and import.
2. For deployment groups you need to connect to source and target repository at the same time. In many customer environments that can't work because e.g. there's a firewall between the DEV and PROD networks.
This is a good reason for me to NOT cope with deployment groups at all.