Like Udey said,Frost is much more powerfull than fire and spike.Since drains enimie stamina and health,also slows him down.Ice storm makes you move with the speed of a Turtle.
Well its not really, its the weakest to be honest. Most enemies are nords or draugrs, they both have 50% resistance to frost. The most powerful expert spell is incinerate (fire) and the most powerful master spells is lightning storm (shock).
It depends what you want though, the novice spells are pretty equal, against a mage use shock, against a warrior (non nord) use ice, and fire has the highest damage due to the burning effect.