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...