FromSoftware honestly doesn't know how to follow basic logic.
With 40 STR, 40 DEX, 10 INT, 10 FTH,
the Bandit's Knife +10 and Blessed LKS +10 have 249 AR and 260 AR respectively.
They both have a LISTED 110 critical number. So theoretically, the Blessed LKS should deal more damage on backstabs and ripostes.
I tested on the Drakeblood Knight on NG+6. With no Hornet Ring, a parry and riposte dealt 516 damage with the Bandit's Knife; 367 damage with the Blessed LKS.
Thank you, Miyazaki.
I tried to control damage types and elements, having both the Bandit's Knife and Blessed LKS deal only physical damage, but I am unsure what type of physical damage criticals deal. Even then I'm sure the Bandit's Knife would still deal more damage.