The 4 most commonly compared Great Katana are (excluding Amanomurakumo):
1. Hagun: 75 DMG, 450 Delay, TP Bonus
TP Bonus effect means it adds 100% TP to your TP when you use your weapon skill. The TP cap is still 300% TP, so a weapon skill at 200% – 300% TP with Hagun would all be the same.
2. Onimaru: 77 DMG, 450 Delay,Latent Effect: 83 DMG
There is a hidden latent effect in this weapon of +5 accuracy and +18 attack. Both latent effect is activated during weapon skill or when TP is under 100%.
3. Ushikirimaru: 82 DMG, 450 Delay, +15 HP, +2 STR, +2 Enmity, Vs. Beasts: +7 Accuracy
4. Shinsoku: 80 DMG, 450 Delay, +5 STR, +1 AGI, -1 INT, Additional effect: TP drain
For a long time, it has been thought that this was the best Great Katana, but when people have slowly figured things out, price has dropped from 10M to about 150k.
I would rank the 4 Great Katana’s in this order:
Weapons Skill at 100%:
Hagun > Onimaru > Ushikirimaru > Shinsoku
Weapon Skill at 300%:
Onimaru > Ushikirimaru > Shinsoku > Hagun
In most situations, you will not be saving TP to 300% before you unleash a weapon skill, so Hagun will probably be most used while Onimaru will be used when you can Meditate to 300% TP before a big fight. These 2 great katanas are all you will need.
Why Hagun is so good?
Even with the low base DMG you can still out parse other great katanas from your higher weapon skill damage. Again I assume you use your weapon skills whenever you can and assuming you only use Tachi: Yukikaze, Gekko, Kasha.
Weapon Skill formula:
Damage = (( D + fSTR + WSC) * fTP) * PDIF
D = DMG of weapon.
fTP = for those 3 weapon skill are 1.5, 2.0, 2.5 for 100% TP, 200% TP and 300% TP respectively.
Hagun weapon skill at 100% TP damage would be (75 + fSTR + WSC) * 2.0 * PDIF. To match this damage with a non TP Bonus weapon at 100% you will need to solve for D in
(D + fSTR + WSC) * 1.5 * PDIF = (75 + fSTR + WSC) * 2.0 * PDIF
(D + fSTR + WSC) * 1.5 = (75 + fSTR + WSC) * 2.0
(D + fSTR + WSC) = (75 + fSTR + WSC) *4/3
D + (fSTR + WSC) = 100 + 4/3 * (fSTR + WSC)
D = 100 + 1/3 * (fSTR + WSC)
As you can see, Hagun weapon skill at 100% TP is stronger than a DMG 100 Great Katana at 100% TP. Do note that all damage have a range determined by PDIF, a low PDIF roll Hagun damage can still be out damaged by a high PDIF roll on another great katana. So do not eye ball a few weapon skill damage to say which great katana performs better. Use a parser and you will see your average weapon skill damage jump compared to others!
Samurai damage comes from mostly weapon skill damage unlike other jobs. Giving up damage over time in the lower base DMG in Hagun is still worth it in the end with the higher weapon skill damage. Assuming you weapon skill whenever possible, saving TP is weak. =P
For obvious reasons, Onimaru is the strongest great katana for 300% TP since you cannot add anymore TP Bonus on Hagun. Onimaru has more DMG, Attack with the sam fTP as Hagun. I usually use this for the first weapon skill for gods and such where you are waiting for people and have time to meditate to 300% TP.
Hagun is the best single slot gear a Samurai can upgrade to. If you cannot afford one, an Onimaru is a great alternative till you can afford one. You really do not need any other great katana besides these 2.