Ice Spear spamming is worse than 1-shot Fireball.
Fireball has a flying time, in which enemies could move and get away from the explosion -Not likely-
Takes one hell of a charging time, and uses 50 MP
Ice Spear is instant, and freezes anybody in it's path.
It has an "infection" like effect
It also uses a lot of MP (How much?)
Spamming Fireball wouldn't be THAT effective, as the most it could probably do is a 500 at rF
And there's also the flying time, once again
Then there's the lag.....