Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
"-layers merge" makes the result just large enough to contain all the layers. One command creates a shadow to the north of the lettering; the other doesn't.
One solution is to add a third layer to each image, large enough to contain the shadow. This will be the largest layer, so the others will fit into it.