Rengoku or TTK

I use portal and currently using both of the sword, but i don't know if i should use Rengoku or TTK for pvp/pve since rengoku seems to deal more damage on the skills because of burn damage, i could be wrong though. I use rengoku to set the factory ablaze and deal most damage, idk about ttk for factory raid

I am wondering what is better, rengoku or ttk. Since i dont know what's the difference