I found that the rack/rail system is similar price between the two. Less then $20 unless(Yakima cheaper) you get the Yakima on a good sale. Its the attachments that BMW was much higher cost then Yakima's. Also the two systems attach differently to the car. Yakima is a door jam system that goes on easy and comes off easy and leaves no marks. The BMW one has the clips that pop up. Im not sure if these are permenatley installed or not (it looks like it). I'm sure someone on here knows for sure otherwise just call you local parts department and ask.

If you go with the BMW rack I believe the Yakima acessories will attach to it.