as far as it goes, mag acc would seem to be the main factor for magical blue magic.. (how redundant to say the whole term) but think of it as normal abilities. EX: Cursed Sphere (says its AOE water damage) is like Waterga. So if you stack INT, more than likely it increases sticking power. I have yet to have a resist on an AOE/fan shaped spell, but that is just me. More than likely, on AOE spells itd say "so-and-so evades" if it was something like Grand slam (which is physical) and just wont do much damage if it was a magic spell. EX: "Suragata casts Cursed Sphere. The Goblin Smithy takes 2 points of damage."
So all-in-all, INT would probably affect it more in the long run because you hardly get any Magic Accuracy+ at lower levels. You'd be better off with more INT gear.
In physical spells, think of it as normal attacks, just dex, acc, and str for corresponding results.