Base diffuse/spec/gloss values are the foundation of a good material OP. If the basic material properties are wrong then nothing else will look right, patterns and details will only muddy things.
In my experience there's no such thing as accurate reflectivity or 100% metalness. That PBR are not physically accurate enough to be perfect at every specific corner of a scene. It's still often not enough shiny at daylight and too shiny at dusk/night. Lots of games still looks kind of plastic while follow all the accurate…
Again, it's a question that doesn't make sense. It's like do you prefer oxygen and toast or water and steak? None of these are mutually exclusive in any way. You should strive to have sound material levels, believable wear, and good lighting and presentation. Let's throw interesting design in there too. If any of these are…