For a light sorc, is it better to have the %light dmg attribute or the %light res attribute? What is considered BIS?

-enemy light resist

I don't understand why? Can you elaborate

you have so much +% to lightning damage already due to mastery that its not as effective as -10% to an enemies resist

when you break light immune with a sunder they end up with resistance near 100%, i forget what "sunder" exactly sets it to, but let say its 90 (i think its 95 but whatever)

so the damage youre actually doing to the monster is 10 percent of what you would deal if it had no resistance

so now lets say you add -10 light res, you just doubled your damage, because now they are resisting 80 vs 90 percent.
and as haseo mentioned the alternate 10% damage is stacking with the 500 percent youre getting from light mastery, its a drop in the bucket, already showing on your tooltips damage.

so negative res is important for making immunes feel like non immunes. Sunder takes them from immortal to mortal, -res makes them squishy

pretty sure thats the gist.