From what I understand, Aedra are generally less powerful than Daedra because they gave up a lot of their power to create the world. Daedra, OTOH, are kind of kind of smugly patting themselves on the back that they get to enjoy the world without having had to give up power to make it. Someone else can chime in where that is found, I want to say it was described this way in something concerning Trinimack.

edit: also, due to whatever contract of creation, Aedra can be killed due to being bound to the "Earthbones" while Daedra can only be banished. Though, the trade off is Aedra can create while Daedra can only change.

It depends on the individual I suspect; Akatosh gave up a good chunk of his power to create the world, but as long as mortals kept the Covenant with St. Alessia he kept large scale Daedric invasions out - so I would say he's at least as powerful as the most powerful Daedric Prince, and probably moreso by a big enough margin that they can't reliably threaten him directly.

And in the Morrowind Chapter, it's implied

Borvath wrote: »

From the Elder Scrolls Wiki, http://elderscrolls.wikia.com/wiki/Et'Ada

Et'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.

That was Magnus and the Magna Ge, not all Aedra. They left after Lorkhan's plot was discovered, but after helping to create Nirn. The Aedra known as the Divines (as well as others like Y'ffre) are those that stayed behind and intentionally gave up their power to complete their creation. Daedra are those that didn't contribute at all to the making of Nirn, with the exception of Meridia who was originally one of the Magna Ge.

King_Kaboodles wrote: »

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?

Sort of.. ish.. Of course the Aedra could never (and would never) visit a plane of oblivion, as they can't physically manifest without an Avatar. While in their own planes Daedra have absolute power, and they have power over their sphere of influence (Knowledge, Destruction, Betrayal, etc) in Mundus. The issue is that because of the covenant between mortals and Akatosh, Daedric Princes can't physically manifest on Nirn either without being summoned by an incredibly powerful summoner. Even then, they are like other Daedra in that the binding is temporary, and they can be banished by "simply" destroying the summoned body. The Daedra do all that they can to try and find ways to influence Mundus, but in the end the Aedra still have more influence because more mortals worship them and despise the Daedra.

If you are talking about raw power, the Aedra and the Daedra are fairly close to equal in Mundus.
If you are talking about influence, the Aedra have significantly more (and that's while not even being able to talk for themselves).

*Side note, no Mundus is not considered Akatosh's plane. If it it any one deity's plane, it would be Lorkhan/Shor. But generally it is considered the Mortal plane, and not attributed to any one Aedra or Daedra.