The D300/700 version snap fits into the same slots as the old plastic ones. The D3s snap fit uses the two slots below the viewfinder and as I mentioned feels a little looser than the D300/700 versions (but it did not fall off or allow dust in).
I just got back from the ANPAT in New Mexico which was filled with dusty condition shooting for 10 days. I removed the three new screen protectors and there was no dust on any of the three LCD screens.
The only possible advantage of the snap-fit over the adhesive version that I can think of is if moisture occurs on the camera LCD.
I am completely pleased with the three protector kits I purchased.