Can I do veneers if my teeth have fillings? Or is it better/safer to do crowns?

I am going to replace the porcelain crowns I currently have on my front 4 teeth. I thought I should do veneers for teeth 5,6,11,12 to improve my smile. However, those teeth have fillings now. So, one dentist told me he'd recommend doing crowns because he the teeth aren't virgin and veneers may fall off or not last long. A cosmetic dentist said veneers without mentioning anything about the fillings. I saw one more dentist who thought crowns'd be better in my case, but he'd do veneers if I wanted.