at lower lvls int is more important but after 50 elemental skill lvl determines main attack power, thus elemental overall matters more but INT is very important.
Actually, Elemental Magic skill lowers the chance of your nuke being resisted (INT does too but in a much lower importance). When you see your spell makes really crappy damage, you know it's been resisted...
Then, if your nuke ain't resisted, more INT will help make more damage. hope this helps...
Elemental Magic skill is a bit more then 1 accuracy for melee and also one magic atk(i think) it basically lower the chance of the mob resisting your spell. 2INT=1 Magic atk, which increases the damage that your spell can deal. EMS>>Matk>>int
For BLM I have alwyas tried to get my Intelligence as high as possible and haven't worried about any other stats. Now I see Elemental Magic Skill and wonder, Is 1 point of Elemental Magic better than 1 point of Intelligence? Is there adifference in which spells are affected by Elemental Magic and which one's are affected by Intelligence?