I can at least say the shield from Nyko did protect my PSP Classic through my first year of college as I always carried it in my pocket but yet, neither of those products were the best and I just ended up using a leather case for eyeglasses in the end.
I mean, you don't need to see the screen when you're playing MP3s. turn the screen off and throw the cover on, you only need the buttons to interact with MP3s.