Basecally this is beacause they were made differently, the Daedra being the blood of Sithis, and Aedra being mixed blood of Anu and Sithis. But what about a guy like Jyggalag who is Order that came from chaos incarnate?
Then one day it hit me.
Jyggalag is neither Aedra nor a true Aedra.
He came from order and represents order.
Jyggalag is THE PURE BLOOD OF ANU!!!
This is why he was so powerful and why the other Princes hated him enough to put aside their own wars and transform him into the most chaotic of Daerdic Princes.
This is all just a theroy of course but it does seem to fit in nicely with everything we know about him so far.
If anyone has any evidence for or against my claims please dont be shy and post them.
Let the discussion begin!