If you are configuring the deployment in Jenkins build configuration you are doing two things
- you are separating the deployment from the project itself and therefore potentially can have different deployments for the same project
- you remove the deployment setup from your version control setup/your source code
If you are leaving it in the pom using the default Maven setup you can run deployment of the project without modification from the commandline on any machine that has the credentials set up correctly. This can greatly help wit troubleshooting and it makes the setup independent of whatever CI server you use.
Both approaches as well as more custom setups like using the Artifactory Build Integration or the Nexus Staging Maven Plugin usage are fine. It will mostly depend on what you are aiming to achieve.
Personally I believe that the configuration should not be isolated to Jenkins and should remain with the project in the pom. But that is just my 2c.