Re: Which ups Orb dmg best: Synergy or FM
To a monster with 0% Cold resistance, Cold Mastery (CM) will increase the orb-damage with +5%. (Not counting the first point that gives -20% to monster cold res), where the Synergy point only adds +2%.
This is true as long as you don't push the monsters resistances below -100%.
If the monster's got some resistance to cold, the scales will tip even more in favor of CM. The higher the resistance, the more the scale tip toward CM.