SSIS Package Configuration types are XML, SQL Server, Environment Variable,Registry Entries and Parent Package Variables.
Security Maintainability Portability
XML: NO No yes
SQL Server: Yes yes No
Env. Variable: NO No -
Reg.Entry: NO No -
Parent Package is used to pass variables value from one package to other and is independent from changes in environment
So by this we can configure the packages according to our need and personally I prefer XML and SQL Server configuration...