title_body: Does the choice of bottle cap or stopper make a difference?
upvoted_answer: I do not think that the type of cork is important. The important thing is that the cork used seals of the bottle so that no wild yeasts or bacteria are able to enter the bottle. 
  
  Traditionally cork and flip-top caps have been used for beers required for preservation, however any seal would do. 
  
  In my opinion it's more about tradition than functionality. Just as with french wines plastic corks can actually provide a more durable seal than metallic caps or real corks as they are less susceptible to decay due to moist. However in the spirit of the tradition and to keep customers happy it's often a less preferred option.
  
  For instance, Belgium is a fairly traditional country and you will often never find plastic beer bottles or twist-top caps. Not because they are up to the task, but just because the Belgians didn't like it.