I am confused about the status of these methods, and more generally about the preferred way to set image attributes in the MagickWand API. It isn't clear whether they do the same, or different things.
Both methods are exported by the Installed API. (6.3.1)
However, MagickSetImageOption is not documented and appears to be deprecated. I notice it was the recommended solution to one question last year involving a PDF processing option.
MagickSetImageAttribute IS documented in the www pages installed with MagickWand, but has disappeared from the online dosumentation pages. There is no indication in the installed API that it is deprecated.
MagickSetImageOption/MagickSetImageAttribute
Use MagickSetOption() to set values before an image is instantiated and MagickSetImageProperty() after the image is created. MagickSetOption() applies to all images created after you call it and MagickSetImageProperty() applies to a specific image. MagickSetImageAttribute() is functionally equivalent to MagickSetImageProperty() but is deprecated.