Defense
As we understand color stacking better it is clear that A.I. defense team heroes - which always have colorless attacks - benefit more from a defense stat emphasis in class nodes and defense stat 3*/ 4* troops since colorless attacks do not get the non linear attack bonus from color stacking.
Attacker
Heroes that gain large benefits from color stacking - Rogue Guardian Jackal, Barbarian Gormek, Sorcerer Sabina, Wizard Kiril, Paladin Sonya, Druid Gobbler, Sorcerer Skittleskull, Ranger Chao, etc. - benefit more from an attack stat emphasis in class nodes and attack stat 3*/ 4* troops since colored attacks do get the non linear attack bonus from color stacking.