The big difference between the wizard and the fighter path through the initial Essentials starter adventure is that the wizard has a lot more power choices to make. This will be true throughout the career of the class, so I think it’s neat that they made the wizard section extra complicated.
In a nice bit of Choose Your Own Adventure design, the wizard battle lasts exactly two rounds. Each round, the wizard chooses between two different at-will attack powers. At the end of the fight, the wizard has used two – exactly two – attack powers. And that’s it: the wizard has chosen all of his at-will powers for the game.
The wizard also has something else to experience that the fighter doesn’t have to deal with: enemies with hit points. The fighter hacked down some minions and called it a day. The wizard, on the other hand, can choose to fight minions or shoot (and be shot at by) a goblin archer with real hit points and real variable damage. Neither the wizard nor the goblin archer will have time to die during the two-round combat, but the wizard learns something the fighter doesn’t: he’s not the only badass in the room.