I haven't tried a glass screen protector but I have heard great things about them for the most part. I'm not sure if I'd like it or not. What I like about the plastic ones (I use Xtremeguard now, used to use Zagg Invisibleshield) is that they are flexible and sort of self-healing. I also like what some people hate about them -- I like the sort of sticky feeling they have when you slide your finger, I guess more of a grippy feeling? I know many people hate that about them but I love it! I do hate the rigid plastic screen protectors, though. I buy the Xtremeguard ones when they have 80%-90% off sales which makes them like $2 or so and that way I don't mind if I replace them a couple of times per year. I haven't had issues with bubbles but we do apply them on our own very, very carefully. My husband is better at the applying the phone protectors while I'm better at applying the iPad protectors. lol
With the glass screen protector, I'd be concerned about scratches a little and if I dropped my phone, would the screen protector shatter/crack?