I never liked the old plastic protectors. Glass protectors have changed my opinion. I have one on my 6 and love it. It has the same feel as the naked screen.
I agree, the glass protectors are much better. But, I've always used a protector, because I carry my phone in a pocket. I try to keep other stuff out of that pocket, but I sometimes forget, and the screen can get scratched or nicked.
I've struggled to put a plastic protector on earlier phones, and never could get it quite right. But, then I tried the Zagg protector. They will install it for you on the spot, for an additional $7.00. With that much experience, he got it perfectly aligned, with no bubbles.
Where I live, there's a Zagg kiosk in the mall almost right in front of the Apple Store. I stopped by, and bought what they called the "HD" protector. It was noticeably clearer than their standard protector, which had an "orange peel" appearance. It also had a smoother "feel" to me.
My newest iPhone is an iPhone 6, and they had a new glass protector, or at least "new since I bought my previous iPhone". It's like the original screen in feel and appearance. It doesn't completely cover the curved glass, but it completely covers the LCD, edge to edge.
Zagg has a lifetime guarantee: they'll replace the protector if it starts to peel up. All you have to do is pay the $7.00 install fee. Also -- I was on my way into Apple to address a problem with my phone, and I expected them to replace it. I stopped by the Zagg kiosk, and they even offered to put a new protector on the replacement phone for $7.00 if I brought them the protector from the replaced phone.
Although the glass protector is tempered glass that is resistant to scratching, I somehow managed to scratch mine. You could only see it from a certain angle and couldn't really feel it. But, I got a replacement this last weekend, paying only the install fee.