I already had a fairly sturdy factory rack on the roof of Subaru Outback Sport (the economy Outback) and was looking for cradles I could attach to that. I originally bought the Rollercoaster for the front and hydroglide for the back with the Fat Mouth Factory rack adapters. Regardless of what the salesman said, this didn't work (Fat Mouths only work with ski racks). So, I exchanged these for the Hull-a-ports (for about $120 less).
You really don't want these on your car at eye/head level without end caps. First, I suspect they'll rust quickly (my old ones rusted even with end caps). Secondly, it's steel that's been cut with a saw- the ends are not jagged but neither are they gently rounded and the covering is shy of the ends by 1/8 inch or so. You hit your head/face on these things and there's a good chance you're coming away bleeding. Third, the ends are ugly without end caps.
Aluminium bars include T-track slots which allow you to use the full length of the bars for load carrying. The WingBar not only looks good but more importantly includes a device which reduces wind noise to the minimum, as well as reducing drag. Many customers leave their Thule WingBars in place from week to week, especially if they are taller vehicles and fitting is awkward.