What's right for you may depend upon what you want to use the bars for. The thread above relates to kayaks. I went for the Thule slidebars which are good. I don't think I could load 2 x 25Kg kayaks without them (and a folding step)!
Other options include the VW bars and Thule aero bars.
There has also been discussion about what heigh feet to get - thule has two options. I was going to get the low profile ones but ended up with the standard because I bought a second hand rack. I'm glad I did as I have a rear spoiler. With the standard height feet I can still open the tailgate with kayaks loaded. With lower feet I wouldn't be able to.