Went with the InCase Snap Smoke, but now have 2 concerns:
1) Case doesn't protrude past the screen, which means no face down glass drop protection
I have the clear Snap case and there most definitely is a lip, albeit a very shallow one. It is safe to put the iPhone face down on flat surfaces. I'm pretty sure the Smoke has the same lip.
2) Dirt/sand getting in between the case and the back of the phone, resulting in scratches.
Again, Clear case here but I have not had any problem with dirt/dust getting under the case and I use it in some dirt/dust-filled environments. I had the case off this morning and the back is still spotless.