Cork allows some contact of the wine with oxygen, allowing it to evolve over the years.
For wines that lose their primary characteristic when aged (think fruity, fresh wines, normally whites) a screw top is the way to go, for something you want to keep in your cellar and let it evolve a bit till is just right, I'll take cork every day.
For wines that lose their primary characteristic when aged (think fruity, fresh wines, normally whites) a screw top is the way to go, for something you want to keep in your cellar and let it evolve a bit till is just right, I'll take cork every day.
As a sidenote, cork was one of the main components of the Space Shuttle's insulation (http://www.nytimes.com/1981/11/03/science/shuttle-s-cork-fro...) [and yes, I'm from Portugal, you can all blame us for the Columbia...]