The L4 and L5 Lagrange points that O'Neill advocated in the 1970s really make no sense.
Halo orbits around Moon-Earth and Sun-Earth L1 and L2 make a lot more sense because they are energetically cheap to get to. L4 and L5 are a ghetto.
Tech like the mass drivers can move material from the asteroid belts in more cheaply than it can from the lunar surface. You also have to consider what it costs to stop the projectiles when they get where they are going (one reason to use the Earth-Moon L1 because you can hit it with nearly no excess velocity)
Halo orbits around Moon-Earth and Sun-Earth L1 and L2 make a lot more sense because they are energetically cheap to get to. L4 and L5 are a ghetto.
Tech like the mass drivers can move material from the asteroid belts in more cheaply than it can from the lunar surface. You also have to consider what it costs to stop the projectiles when they get where they are going (one reason to use the Earth-Moon L1 because you can hit it with nearly no excess velocity)