I've got both the fenix 5 and 5S for testing and choosing between them was initially difficult.
The 5 glass version is too big for my small wrist. However in slate grey it looks high quality. The buttons are also fantastic and feel high quality.
The 5S glass version is cheapened by the silver bezel. But the buttons really are poor quality and don't provide the definitive feedback - they feel 'cheap', sadly.
However, given the size of the 5S I will be keeping this one instead of the 5.
The design of the 5 is better overall, which is to be expected, as it's the main seller in the range. The 5s being the same price is scandalous, as it's nowhere near as high quality in buttons, materials, etc.