I agree with what the others says; If we try to take the weapon, militarily we will lose a lot of ships and troops fending off the other factions seeking to destroy it, politically like what was stated we'd become enemies of the other factions and a cold war might even begin between the light sided factions and us.
If we attempt to destroy the weapon, I still believe we should get some information regarding it as this is no bloody time to be modest, the other factions would do the same. But there, if we attempt to destroy it, we wouldn't lose additional forces in the ensuring skirmish with the other factions, and politically we'd be rather golden for a dark sided faction, and as someone said, cement our rule as Galactic Leader.
I think our best case scenario might envolve "giving up" the superweapon (We might be able to build something with that information, perhaps a flagship.), to increase relations and whatever political stuff you guys have, I'm only a navy captain don't listen to me.