I've used both the ZAGG and SGP screen protectors on my RAZR. Here are my opinions:
- ZAGG: Unscratchable, but makes the RAZR's display very grainy, IMO. Does not smudge much. The protector has the usual ZAGG "rubbery" feel -- I don't mind it, but some people might. The protector covers just about every inch of the RAZR's front (other than the openings for the camera, microphone, and LED indicator). Installation can be tricky if you haven't done a ZAGG screen protector before. ZAGG only includes 1 screen protector in the package.
- SGP (Ultra Crystal): Smudges easily, and also does show scratches over time. But it feels like it isn't even there, and it does not detract from the RAZR's beautiful display at all. The protector covers probably 90-95% of the RAZR's front (there will be small unprotected areas of the outer bezel on the top/bottom/left/right). Installation was a snap -- I got it right the first time. SGP includes 2 screen protectors in the package.
For what it's worth, I like the clarity, feel, and ease of installation of the SGP, but prefer the durability of the ZAGG. So you can decide which attributes are most important to you.
For anybody doing their first install of a screen protector, I recommend spending some time with YouTube, watching videos of other people's installations.