What is the difference between a *.lyr and a layer directly added from *.gdb/sde to mxd?
Doing it difference in mxd?
Which is better?
A layer file can store information about how you want one or more layers to look. This includes symbology, labeling, display scales, definition queries, etc. If you add a layer directly from a geodatabse or SDE layer, you get the default symbology (generally speaking). In this respect, layer files are better/more useful.