I googled a NASA page and came up with the Southern Hemisphere having a slight advantage right now.
Our orbit is elliptical and the Earth is tilted with the Southern hemisphere nearest to the Sun at the time when we are nearest to the Sun. There are other meterologic reasons why the South might get less cloud cover, too.
The Earth has a wobble on its' axis and the tilt might be either advancing or retarding which could be why HP qualified his question with a 100 year limit.
Now I await the "trick" answer........
