I use a clear protective film on the screen, and a full silicone cover over the rest of the phone. In 18 months of iPhone ownership, phone is completely scratch/dent/mark free, and it doesn’t get treated lightly. Goes everywhere with me, has been dropped accidentally a few times. My old Nokia looked like it had been driven over by comparison, I am not known for looking after phones!
Only issue with the silicone case is that it’s grippy, so makes it harder to slide the phone in and out of tight jeans pockets say. But if you don’t wear trousers with mega tight pockets, then no issues really.