This year for Xmass I bought a friend of mine an Evolution 4 car cover for his 3 series from Auto Anything. It is an excellent value at 160.00! The Noah is a great cover as well. The nice thing about the cover from Auto Anything was that it was custom fit meaning cut to fit your particular model. My buddy claims that it fits perfectly and is so soft on the inside that it wont scratch the paint... also it has a very good level of water resistance while being breathable. Auto Anythings site had excellent comparisons of the features and benefits of the different covers. This may aid in your final decision!
http://www.autoanything.com/car-covers/10A50166.aspx
Best of luck.