Which Fighter (TWF Fighter vs. Great Weapon Fighter) is better optimized for Dealing Damage?

Question

With Basic's release the Fighter is given six different Fighting Styles to choose from at level 1. Each fighting style offers a solid mechanical benefit to the fighter, but both Great Weapon Fighting and Two-Weapon Fighting leapt out at me as providing the strongest mechanical benefit.

Great Weapon Fighting When you roll a 1 or 2 on a damage die for an attack you make with a melee weapon that you are wielding with two hands, you can reroll the die and must use the new roll, even if the new roll is a 1 or a 2. The weapon must have the two-handed or versatile property for you to gain this benefit.

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Two-Weapon Fighting When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack.

At level 1 which feature is optimized to deal more damage? Which at level 20?

Answer 1

At L1, Two Weapon fighting (TWF) is more optimized. At level 5 the preference switches to Great Weapon Fighting (GWF).

Let's look at why. We're only going to go with a brief snapshot here of L1 and L20. I'm going to assume that Str is 16 at L1 and 20 at L20. Our TWF will wield dual Scimitars (or short swords), and our GWF will wield the Maul or Great Sword.

We'll use the Ogre from the starter as our jousting dummy at L1 (AC 11) and the Nothic (AC 15) at L20 (the Ogre is a near auto hit and thus relatively uninteresting for this particular comparison). The hit chance for our L1 bout is 75%, and the hit chance for our L20 bout is 80%. When a better study of monsters is available to me, I'll update our hit chances here.

To explain the concepts here the TWF gets to add their stat bonus to their bonus action attack, whereas our GWF gets to reroll any 1s and 2s on their first pass of die rolls. We'll be using the following formula for the average die for the GWF:

\$ \text{Avg}(2\text{d}6) = 2\left( \frac2 6 * 3.5 + \frac4 6 * 4.5 = \frac{25} 6 \right) = 8.33 \$

To calculate crits in 5e, you simply multiple the dice rolled by the crit chance. Since nothing is maxed, there is no need to subtract the crit term from the main roll in this edition.

L1 AC 11:

\$ \text{GWF}: 2\text{d}6 + 3 = 11.33 * .75 + .05*8.33 = 8.914 \text{ DPR} \\ \text{TWF}: 2*(1\text{d}6+ 3) = 2*(6.5*.75 + .05*3.5) = 10.1 \text{ DPR} \$

As you can see, at L1, the TWF has an edge of about 1 DPR. Let's look at L20. At L20, our stats go to 20, the fighter makes 4 attacks per round plus the TWF gets his bonus action and the crit range is 18-20 or 15%. Our attack bonus is +11 and our hit chance is 80%

L20 AC 15:

\$ \text{GWF}: 4*(2\text{d}6+5) = 4*(13.33 * .8 + .15 * 8.33) = 47.65 \\ \text{TWF}: 5*(1\text{d}6+5) = 5*(8.5 * .8 + .15 * 3.5) = 36.63 \$

At this point the TWF is heavily outclassed by the GWF. It's not even really close. It becomes a bit closer when the hit chance is lower. But, ultimately, the problem is that the TWF only ever gets that single bonus action attack, and it's not going to be enough to compete with the GWF's big single attacks.

Answer 2

TL;DR Great weapon fighting will provide you more consistent damage and will do so in just as reasonable, if not larger, numbers than two weapon fighting.

More detailed answer

1. TWF: one extra attack per round. This is useful, but is limited to d6/d8 weapons depending on feats. You're a fighter, so we'll assume you grabbed the feat for it. At level 20, you'll deal a maximum of 9d8 + 45 in a nova round (hit with all attacks). You could use Magic Initiate(feat) to grab hex, or have a party member give you inspiration, etc, but 86 average damage in a maximum nova round. This does not count Attack of Opportunity, as you can't rely on it.

2. GWF: you've got options for 2h weapons, but your best bet is either a maul or a greatsword (see below). The bonus that great weapon fighting gives you is the ability to re-roll a 1 or a 2 on a die, taking the new roll no matter what.

   • Example: greataxe,(1d12). You can effectively treat it as a d22, with the numbers 1, 2, 3, 3, 4, 4, 5, 5, etc. That's cool, as it halves your likelihood of rolling a 1 or a 2. We have better options.

     • Here is where the maul improves damage. 2d6 is basically 1d12+1. With GWF, you have a chance of rolling a 1 or a 2 with both dice. So you're rolling a 2d10 with the numbers 3-6 written on them twice in lieu of 7-0. Why is this so good?
   • Your great weapon fighting bonus can be used twice per attack, if necessary. This doesn't raise your minimum damage, instead, it raises your average damage by a substantial amount. Your average nova round yields 92 damage.

3. Is it that big of a difference? That's only a 6 dpr difference between the two at level 20. That wasn't taking into account that the min/max's for TWF is 54/117 and that the min/max for great is 56/136. This gives a great weapon a larger spread, yes. But it also gives you higher average, and therefore a more reliable dpr.

   • The one big thing that I haven't taken into account is that, with a ninth attack roll, the chance to crit is increased by 1/9th. Across infinite successions, that means that TWF is 11% more likely to crit. When coupled with a Champion archetype, this could boost your nova damage top end. I don't really think that level of detail is what you were looking for.

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Bottom Line: Pick the one that suits your concept of your character better. They're so close to each other in damage after taking potential critical hits into account (within 3 points of average dpr after crit potential)that it's really not worth fretting over.