I want to get a M2 weapon but i am very confuse... Maybe you could help me ! Now I am second lieutenant and i dont know what to choose... To get isida m2 right now... To make the level for railgun m2... Or to make 2 lvls and get thunder m2(which i understand it's pretty strong)... Please help me

What do you like more... Isida m2 or railgun m2 ? And I would like to know their benefits and disadvantages. Thanks :*