Generally EA is stronger. Its easier to use and not so situational. Also the 1 minute CD is just insane.
Perception on the other hand comes in handy if you are a warlock playing with felhunters panaroia. 20 to 30y range stealth detection is pretty intense.
For mage, take EA. You got it ready almost every time you need it, are able to escape other mages shatter combos and so on. As a bonus you also get 5% more int from gnomes.
Gnome/Mage is the strongest Race/Mage combo in the game.
Peace