I only have experience with InvisibleShields on my iPhones. It's an alright product. I don't like how it makes the screen look though. If you look closely at it when it's applied, then you can see what appears like some of the solution between the screen and the protector. It looks like tiny little specs and this rainbow effect. It's not too noticable, but it's there. Also I like the smooth feel of a screen without the protector, and the InvisibleShield makes it feel rubbery and makes it difficult to slide your finger across. It appears to attract more grime to it too, so I was constantly wiping it down with a damp cloth.
The one I applied to my white iPhone also ended up turning yellowish after a couple of months from use. But once I removed it, the phone was pristine and white. They work well to protect the device from scuffs, but I just don't like the feel of them on, so I ended up removing them from both of my iPhones. I also think they're overpriced considering they're just a simple sheet of plastic.
So overall, I felt that I'd rather live with a tiny scratch that may slightly affect the view of my screen than constantly dealing with a rubbery screen protector that makes the screen look different.