From the Elder Scrolls Wiki, http://elderscrolls.wikia.com/wiki/Et'AdaEt'Ada, also called the "Original Spirits", are the things perceived and revered by the mortals as gods or spirits. To humans, these et'Ada are the Gods and Demons. To the Aldmer, the Aedra (Aldmeri translation is "our ancestors") and Daedra (Aldmeri translation is "not our ancestors"). The Aedra and Daedra came to be once Lorkhan convinced/tricked the Original Spirits (et'Ada) to create Mundus. The Daedra are the descendant spirits of the et'Ada who left during the creation of Mundus to retain their power. The Aedra are the descendant spirits of the et'Ada who remained during the creation of Mundus, thus giving away a significant amount of their power.Aedra and Daedra are like factions of the same race, the Et'Ada. Their differances are that the Daedra tried to preserve their power and left at the start of the creation of Nirn, while the Aedra left creation of Nirn later. The Aedra teared holes in the sky to escape to Aetherius, which are the stars and the Sun.
So is it fair to say that since a daedra is way more powerful in their own plane of oblivion. A aedra like lets say akatosh is way more powerful on Nirn which could be seen as his plane?* So on nirn Akatosh is more powerful than Molag Bal but if akatosh goes to coldharbor then its vice versa?