In my personal opinion, tempered glass is the way to go for a screen protector. I have found that these work the best to protect my phone from cracks and scratches. I am quite a clumsy person as is and in all my years of having an iPhone the only time I've ever cracked one is when I literally threw it to the floor and it cracked just the top corner. But it literally flew out of my hands at a really fast speed, which I think is what did it.
I am the kind of person that drops my phone probably once a day, if not more to be perfectly honest.
Tempered. Glass. Works. I am the biggest advocate for it because they work for everything: like protecting against scratches, drops, and falls.
I prefer to replace my tempered glass every couple of months, or as soon as it has any visible signs of wear and tear. If you drop your phone, chances are that the tempered glass is going to break (hence saving your phone), and this is when I will go ahead and replace mine. If the top or the corners chip a little bit, you can probably wait it out, but the bigger the crack, the bigger the chance of the next drop damaging your phone.
Tempered glass can get expensive, but I'm going to be honest with you. They are all the same. The $10 tempered glass we sell is the exact same as a $25 tempered glass you can get at Best Buy (or any other electronic store). It is not worth paying the extra money for something that is going to be the same irregardless of where you purchase it. The only place I wouldn't recommend buying tempered glass would be the dollar store, if they even sell them. There's no way that crap is up to par.
We sell our own tempered glass for $10 at our Shopify, which you can find here. Check it out and pick up one or two (we have a deal if you buy two). Let me know what you think about tempered glass and what your favorite way to protect your screen is!
Dojo Master Ken