In Pathfinder, what is more likely to deliver a critical hit:
- Attacking once per round with an Elven Curve Blade (critical threat range 18-20)
- Attacking twice per round with Two Weapon Fighting (TWF) and two light blades, such as two short swords (critical threat range 19-20) but at -2 to hit
I am working on an Eldritch Knight (EK) build. I'd like to understand what is more likely to deliver that Spell Critical in a full attack: attacking twice per round at -2 on a threat range of 19-20, or attacking once per round on a threat range of 18-20.
I am looking for a way to graph these two probabilities against a range of Armor Class values.
I understand that the TWF is only applicable in a Full Attack. For the purposes of this question I'm only interested in a Full Attack.
I understand that there are other ways to increase a threat range or attack more often. For the purposes of this question I'm not applying haste nor keen edge nor strength bonuses nor any other bonus to attack. I'm also not going to use a kukri (light weapon, threat range 18-20) in this comparison.
If it makes a difference, the EK is Fighter 1, Wizard 5, EK 10. That would make a Base Attack Bonus of +13 (1 + 2 + 10).
EDIT: The EK has the Two Weapon Fighting feat and both weapons are light. The modifier is -2 for each attack: primary hand and off hand. The EK does not have the Improved Two-Weapon Fighting feat.
I'm assuming that the opponent would have an AC of 29, so the additional attacks at +8 and +3 would only hit on a roll of 20 and therefore not make a difference to the probabilities. I'd take two twenties in a row but I understand (1/20)^2 is only 0.0025 likely to occur.
I'm interested in knowing how the probability changes over a range of Armor Class values below and above 29, but to help narrow the question I've picked one AC.