Whats the best long gun

I've use the 3 best long guns, the nashkar the piquere 3 and the divine thunder and while I use them on my Garuda I see no real damage difference besides for the numbers on the gun itself because each gun is doing about 4000 to 5000 damage regularly while you Mike get 6000 but I see no difference other than one doing poison one doing fire and one lightning. What do you think is the best for pure damage.