My understanding is that 1% intelligence translates into 1% spellpower. I know that intelligence also gives you more crit, but lets set that aside for the moment.
The damage increase from 1% spellpower should vary based on the base damage of the spell being cast. But I don't know what the formula is for calculating at which point spellpower is greater than spell damage.
To sum it up, Is Intelligence > spell damage? if so, is there a break point where spell damage is greater?