Everything effects everything....

With more weight (trunk) in the rear with the same spring rate, the higher weight will handle the bumps better as will the softer seat on the GL1800. You'll perceive it as a suspension upgrade on the full wing. If you run light on the F6b, set your spring rate lighter and you can almost match the "feel" of the suspension to the Gl1800. You'll of course get a little more bounce to the back end on the f6b because you are in fact much lighter back there than the GL1800. It's a feel thing I think more than anything. Personally the stock suspension on my F6b is the best I've ever ridden on coming from riding Harleys.

I agree fully that the F6b puts out more attitude in the looks department being a bagger. It looks fast, sleek, long and low. It begs more attention from other riders and most cyclists know full well that the GL1800 motors can flat out stomp when they need to. Add that knowledge to the visual appeal of the low slung bagger and it's given a little more street cred and respect.