Which vacuum cleaner has the best suction?

Since the introduction of the new EU product labelling requirements in September 2014 manufacturers now need to state the effectiveness of their products at picking up dust from both carpeted and hard floors. This means that you can compare different products to see which has best suction. Take a look at the screenshot from ao.com’s website below to see how this info is displayed. In each case A is the highest level achievable and G is lowest.

Picture of ao.com's specs for new vacuums