Fighter weapon choice;

[Varashad]

I have a +5 Flaming Burst of Pure Good + Icy Burst great axe, and a falchion with the same details. I am a kensai half-orc. Which of these two weapons will deal better damage until I pick up a green steel greataxe? I know that versus 0 fort, falchion wins, and with 10% or more fort it's all great axe, but then, what monsters have fortification? Is it only red/orange/bosses, undead, constructs, etc, that have fort, or does that Bearded Devil and Ice Flenser also have fort?

Also, I am planning on making a green steel great sword for both trash and boss smashing(lit II). Is there any reason I should use a great axe instead?

[assimilateur]

Crit effects seem to proc even if the target is immune to crits. I mean, my stonedust wraps petrify zombies no problem, so I expect your elemental bursts to do the same. Accordingly, elemental-burst falchions can reasonably be expected to be superior to great axes even against crit-immune mobs.

[Kinerd]

For randomly generated weapons, it is more difficult for greataxes to catch up due to fortification. The base damage dice advantage they have over the falchion is only 6.5 to 5 = 1.5, as compared to 10.5 to 7 = 3.5 for green steel. This means that our equation is:
(16 + 3 * 3 + 19 * .75 * .5) * (6.5 + x) + 2 * 3 * 11 = (12 + 7 * 2 + 19 * .75 * .5) * (5 + x) + 2 * 7 * 5.5
x = 32.1875
For all damage bonus 33 or higher, you do more damage overall with the falchion.

Alternatively, we can set a damage bonus and solve for fortification. As a half-orc THF kensei, we conservatively have:
4 half-orc
8*2 power attack
18*1.5 strength bonus
4 kensei
2 fighter enhancements
4 fighter feats
=
57 damage bonus

Now our equation is:
(16 + 3 * (3 * (1 - f) + 1 * f)) + 19 * .75 * .5) * (6.5 + 57) + 2 * 3 * 11 = (12 + 7 * (2 * (1 - f) + 1 * f) + 19 * .75 * .5) * (5 + 57) + 2 * 7 * 5.5
32.125 * 63.5 - 6 * 63.5 * f = 33.125 * 62 - 7 * 62 * f + 11
53 * f = 24.8125
f = .468
Effectively, for all fortification lower than 50, the falchion will do more damage with your (hypothetical) damage bonus. The more your damage bonus increases, the higher fortification is required for the greataxe to catch up.

.

Regarding your green steel great sword, a lit 2 is not a good choice for THF boss smashing. Magical effects are much less likely to go off on glancing blows, but glancing blows are subject to full DR. Additionally, not all bosses take full damage from electricity. Your best bet outside of an eSoS with the proper crystal is to make or commission a +4 (/+5) Holy (Burst) of (Greater) Whatever Bane.