i actualy tested damage reduction and its value vs defense, both lvl 7 gold chakras on average the damage reduction rune against an opponent with 500 power less than me reduced the attack damage i took by 240 a hit, defense reduced damage by 200 per hit

whether the stats will change in which is better to stack as i get more or not i dont know and didnt bother testing but with 6200 defense and 1150 damage reduction before the runes, the damage reduction rune is alot better since it will reduce nin damage too and the physical damage is about the same

damage reduction reduces all damage taken not just damage from when ur effected by chaos

point for point its worth less than defense/resistance but it reduces both types of damage

so when u use the 8 gates chakra for damage reduction which has almost 3x the amount as resistance/defense you actualy get alot more reduction plus they stack