If you insert DCs then they are automatically made unique by design, so editing the attributes of one only affects that one. Unless you have nested DCs... when the unique containers could then contain repeated versions of the same DC, which of course will change globally should you edit any of that DC's attributes in one container.
A DC that is copied in a model will be just that - a second instance of the same DC - so editing one will then change the other too - but that is useful if you have six identical widgets and you want to change their manufacturer en mass.
So have attributes you want to remain unique attached to the container DC so each unique instance has unique attributes, and conversely any attributes you might want to capable of change en mass should be attached to a nested DC, so then changing one will ripple through to several.
