I'm assuming you mean an outdoor cover.
A mate of mine is a part-time trader and uses covers on a lot of his cars.
But if they aren't a really snug fit, when it gets windy they can rub the paint on the tops of the front and rear wings.
Based on that, if I really had to have one I'd probably opt for part roof - which has the added bonus that you don't get "curious" people lifting the cover to see what's under it!
Mine just lives outdoors "au natural". :lol: