What's the difference between the various registration methods listed in Slicer?
Most of the registration modules use the same underlying ITK registration algorithm for cost function and optimization, but differ in implementation on parameter selection, initialization and the type of image toward which they have been tailored. To help choose the best one for you based on the method or available options, an overview of all registration methods incl. a comparison matrix can be found here.
To help choose based on a particular image type and content, you will find many example cases incl. step-by-step instructions and discussions on the particular registration challenges in the Slicer Registration Library. The library is organized in several different ways, e.g. consult this sortable table with all cases and the method used.
There is also a brief overview within Slicer that helps distinguish: Select the Registration Welcome option at the top of the Modules/Registration menu.