Definately Wix. :)
Wix allows you to do the most things with ease and the difficult things without hacks, it's free and open-source.
You can use Wix within Visual Studio (using Votive) or you can use it using the .Net SDK, MSBuild and your favorite XML editor. Wix supports creating MSI installers, MSP patches, MSM Merge modules, Wix libraries and much more.
