Ghost armor is by far the best. Not only do they offer a better quality screen protector, you also have the option of a full body protector. It covers the screen, speakers, top and bottom edges and the back. It comes in a clear, matte, or carbon fiber finish. You have different color choices with the carbon fiber as well.
I had a Zagg up until recently. It worked great and was by far the toughest I have ever tried out. The only thing I didn't love was the slight "orange peel" look across the surface. Sensitivity wasn't affected too terribly.
When I cracked my screen recently (one horizontal line across the very top), I said "F it I'm free balling it". I took off the case and the zagg screen protector. In gonna get it good n messed up before I do an Insurance claim. Only, it's been naked for 2 months or more, and the screen is not scuffed yet.
My vote for best screen protector would be for one of those glass ones... As long as it's not crazy expensive. I saw some guys talking about them over on another thread- so I have no first hand experience.
I have one on my phone, and I'm never going back. They are extremely durable and just down right beautiful. The Mime glass ones are around 20-27 I believe.