I have the ski bag on my 5 and don't like it. My wife only has the fold down seats in her 3. I still use my old nylon ski bag even in my car. It is much easier to clean and I just buy a cheap new one if it gets too shabby after a while.
Also when going into a hotel and dropping the skis I can carry 2 sets in my bag. Also with trunk space I actually prefer to take 1 seat down and put the skis to one side and have more space for a suitcase.