Information about ASP.NET MVC bundling is here: http://weblogs.asp.net/scottgu/archive/2011/11/27/new-bundling-and-minification-support-asp-net-4-5-series.aspx.
ASP.NET is adding a feature that makes it easy to “bundle” or
“combine” multiple CSS and JavaScript files into fewer HTTP requests.
This causes the browser to request a lot fewer files and in turn
reduces the time it takes to fetch them.The next release of ASP.NET is also adding a new feature that makes it
easy to reduce or “minify” the download size of the content as well.
Looks like it’s essentially the same thing as Cassette. All other things being equal, use the solution that is native to ASP.NET MVC.