For "scale" and "freedom", theoretically, you could build as many O'Neill cylinders as you want (there's lots of resources in a star system), and make them quite large. What's easier about planets is that you don't have to have this technology or go to this trouble, but the problem is that in reality, there just aren't any habitable planets out there within a reasonable distance, except the one we're standing on right now. If we discovered warp drive or some alien stargates or something and could easily transport ourselves to countless distant star systems, that might be different, but right now it isn't.