The difference is you get an easier start with an Altmer. BY FAR. 5 extra levels of magicka which his great for beg/mid game. Not to mention Highborn which is great at EVERY level. Altmer are cleary the best choice for mages this time (unlike oblivion where the Bretons were clearly favored) and Bethesda makes sure you know it.
Well it's not a by far since they're still the biggest pushovers when it comes to defense, they have nothing to protect themselves against anything. They have no defense against weapon, arrows or spells, they're glass cannons. They can out put the most spells but they're the only race with literally nothing to help with survival. Even Red Guard has 50% poison resistance. Breton has insane protection against spells, orcs take half damage from everything when they battlecry, Imperials get a fear power, Khajiit can flee faster... etc etc.