We have side screens on most of the time - SWMBO really doesn't like motorways or mountains without them.
My preference is always roof down whenever possible - the visibility around the car is restricted with the roof up so I feel safer that way. I had a lot of years driving high mileages and have only once had anything hit the car above bonnet height - a bolt dented the roof of a Ford Orion I had briefly. If the car had been topless it would have hurtled past without touching.
My one concession is that when I see a tipper lorry with bits falling off I give it a very wide berth.
