This is a question I ran across recently while browsing the SSIS 2012 pre-lease forum. While there may be multiple ways to look at the differences and similarities among them, I thought I would give it a shot and share some of my observations.
If you are familiar with earlier versions of SSIS, it is worth noting that the concept and usability of variables have not changed much in the newer version. on the other hand, it is also important to point that parameters are one of the new features introduced in SSIS 2012 – available when using the new project deployment model - that promises to address some of the shortcomings of package configurations – which are still available.
ScopeParameters can be defined at 2 different levels:
Project. These type of parameters are available to all packages within the SSIS project. Think about them as global parameters. They come handy as it makes really easy to share a given value, such as the path to a file share or the name of a server, across all packages in a project.Package. These type of parameters are meant to affect only the package on which they were defined.
Variables are richer in scope as they can be scoped at the package, container, task or event handler level.
Execution Time behavior
On the other hand, the value of variables can change during the execution of the package, which make them suitable for scenarios where, for example, looping, conditional or any other type of logic where the values of the variable must change during the execution of the package.
Consumption and Usage
The value of a variable can be set in many ways within a package and its value can be further referenced by other expressions, containers, tasks or components.
Note: Expressions are not new to this version of SSIS and something you should put in your short list of things to learn if you are serious about SSIS.
Visual Studio Configuration Manager
I am pretty sure there may be more aspects to parameters and variables than the ones I listed here, so feel free to leave your feedback in the comments below with anything I may missed.