The streamline tubing is .049 which is about 17 gauge, Jacks are .065 which is almost 14 gauge so it is thinner. I am not sure of the significance of it's thinness.
Yes it is more expensive but in reality you are only buying 4' of the stuff so we are talking an extra $100. Sure it's not the "locost" spirit but neither is IRS or Wilwood anything.
As I understand it the aerodynamic gain in 1x2 rec is having a smooth long surface along the path of airflow. the fact that it has right angled edges is not part of it's gain, the fact that it has a longer cross section parallel to airflow is. It's just an assumption but my guess is that streamlined tubing built for planes is more... streamlined
Don't get me wrong, I think the "gains" of using this stuff is limited at best, however (and this is no offence to Jack, I love those lower control arms, they take the spirit of form and function further than most things) I think they just look a little dumpy. I was debating the merits of chroming them to make them look smaller but then I stumbled upon this stuff which compared to chroming the arms is cheaper.