Overall construction and rigidity. I can't say much about durability for the obvious reason, and I most likely won't since I don't abuse my stuffs.
I've not seen the Porsche sunshade one so can't comment. I just disliked the fact that I am "advertising" a Porsche...a Porsche. I don't care about what other people think but it's just me. I see enough Porsche badges on the car. I want to keep it as clean as possible in terms of aesthetics.
Also, I don't like the roll type. Fold-type is the way to go IMO.
Not much to say about anything else. I mainly wanted to cover up the amount of interior exposed to direct sunlight. I may not keep my car for very long...thinking about GTS already. >