The Noctua runs cooler at both idle and load but no more than 5C and it's also noticably quieter [by like 7db]. The Noctua is clearly better performance but you didn't list the prices. You have to decide which one is worth the money. Personally, I would go with the Noctua if the price difference isn't much.
The price difference is like $30. I would say it's money put to good use if you want a quiet system. Here's the links: http://www.guru3d.com/article/cooler-master-v6-gt-review/10http://www.guru3d.com/article/noctua-nhc14-cpu-cooler-review/9