Iron Will vs Elemental Focus

Hey Exiles

Which of the mentioned gems at lv20 will greater increase damage of Incinerate?Assume my char chas 300 STR.
So basically it's 98% increased vs 49% more.Which is greater?Tried to calculate that based on PoE Wiki,but either IW > EF,or I did calculations wrong.

That depends on how much increased damage you have from other sources. The breakpoint with those percentages is 100% increased damage; if you have more than that, then the 49% more modifier is better, if less then 98% increased is better. Most builds have several hundred percent of increased damage from tree alone, so likely you should go with elemental focus.