Personally i wouldn't recommend one, unless you take it off like once a week to clean underneath it. My mom has one on her car, and she never took it off when she washed the car now she has some nice rust spots on her hood where it was.
As long as you clean underneath it regularly i think they are great to have. Just my opinions.
The only reason i am using one is because of the hood damage, my mom bought me the hood protector, so it was cheaper than a new hood, and if the hood rust who cares, I'm getting a new one anyway.