[STEVE-O]

I know winter has finally past and here in the NorthEast, cars from storage are finally getting back on the road. However I have a question related to winter storage.
I saw in the California covers catalog, a car storage bag intended for long term storage, where the car is driven onto and then its zippered close.
The bag cloth is also treated with a rust preventative.
Has anyone used this type of car storage bag? Would it work in keeping moisture from condensing on the car?
Is a zippered enclosed bag any better then just having the car sit with just a normal car cover on it?
Any thoughts?
thanks