Second had Thule are fine in theory – my brother had his Thule bars on his car for 10 years during his surfing and windsurfing days so spent most of their time near the coast exposed to the salty air and moisture and after all that time the car dissolved and the Thule bars came off and after a bit of spit and polish came up like new and were sold on for nearly the same price he bought them for. However, you’ll probably find that they’re not that much cheaper than brand new depending on the car they’re for, so may as well go the little bit extra and get brand new. Worth checking out though.
As for aero, they’re only worth it if you’re keeping your bars on the roof permanently – they’re only quiet when nothing is attached to them – as soon as you start putting roof boxes and bike racks on them then the majority of the noise and drag will come from the attachment so may as well cash in on the cheaper price and easier fitting of the non-aero bars.