Dave
Both will work, the main reason to use a module:
The module only has stuff on the layers which were visible when saved, so you do not need to bring in additional stuff you do not want. (which might clash with stuff in your 'host' file. ie if both files share layers such as text & dimensions but the orientations are different or the scale are radically different)
The main reason to use a project:
Auto-update each time the source file is saved, the host can read it in (less hassle)
Whichever you use a bit of project planning is wise
regards