Styling is all about personal preference. Having said that, my last car was a 545i with the sport package/shadowline trim in orient blue and i currently drive the GS350 in opaline pearl. I think both cars are attractive but I slightly prefer the look of the BMW 5 series with shadowline trim over the look of the GS350 with the chrome accents.
However, I've been getting more admirers and positive comments from strangers than when i was driving the BMW. I think this is due to the fewer number of 3rd gen GSs on the road in southern california vs. the bmw 5 series and also because the color i'm driving, opaline pearl, looks exceptionally good on the GS350.