Note that if those heroes have the same star, the increase in attack and defence will equal percentage wise, in your example, the attack is increased higher percentage wise.
Let me give example with slash damage of Ametrine against Sudri:
No-LB Ametrine against No-LB Sudri
Slash damage = 100 ร (716 / 484) ^ 1.35 = 169
Sudri HP left = 775 - 169 = 606
LB Ametrine against LB Sudri
Slash damage = 100 ร (778 / 549) ^ 1.35 = 160
Sudri HP left = 878 - 160 = 718