They are very good for security & if you get the long one that goes over the bonnet then rain is kept off the engine. In the 4/4 that means the holes for the plugs do not fill up with water.
I have John Taylor one.
But don't use them on a dirty car or the wind will move the cover & scratch the car.
This isn't my car but you can see you can use them without putting up the roof.
