i dont use es-net! and i use my net util ! so put Spatial in EntityData is convenient than use map.put(entityID,Spatial )
its just one question over 1000 questions how ES should be done to work well. If you stop on this question i belive you should look/use ready solution:
Putting a spatial into EntityData is like storing a JTextField into an Oracle database.
convenient or Normative standard who have more values?
Only data goes into entity data. A spatial is a visual representation of data. It is not data itself.
You probably just want a transform component or at the very least a location component.