Personally, I’d say external aspects, because as you are dreaming you automatically see the external dream world, while it take conscious effort to check how you are feeling at that time. Hope this helps!
It depends on how many of your typical DS are external or internal. For example, if your dreams are characterized by pink flying elephants or people acting really strange, dreamscapes changing their appearance etc, you should pay more attention to the external aspects. But if you frequently feel odd in your dreams, decide to do things that you normally wouldn’t do or have unusual emotions, focus more on the internal aspect.
Well the point of LL is to become completely aware. So in my opinion the both. You need to find the right balance between the 2 and with time expand your awareness on more and more things.
That’s something what is in Buddhism called enlightenment…