title_body: What's going on inside a Nespresso capsule?
upvoted_answer: Well, as you have yourself conclude that they have no difference regarding the amount of coffee (6 g). I just gonna put there an important note that some people miss.
  
  Espresso capsules are made to be extracted as espressos and lungos, as lungos. The point of this is that Nespresso's lungo coffees are supposedly designed to have a more balanced flavor over a longer extraction/more diluted in contrast to the espresso which was made and evaluated to be drink in a single, stronger shot.
  
  As for myself, I had both ways already and I do believe that at least for the espresso capsules, stick with espresso size (especially if you are using a 3rd party capsule). Nespresso's lungos are often too watery, in my opinion.