Personally I prefer metal casing because it feels more premium.
I also really enjoy taking my Surface in the morning and touching this nearly cold magnesium. I don't know exactly why, but cold surfaces gives a nice feeling imo. (maybe cause a PC becomes hot when it has hard time and the heat is a deperdition/waste of energy - so perhaps in my mind there is a little voice who tell me that when it gets hot, it's not good)
The other element that gives a sense of well-build device is unibody design.
I prefer not seeing at those junctions between pieces of hardware.
Perhaps the word that give a sense at all those things I've said (metal, cold, unibody) is: industrial design.
Yes, I like devices that feel raw (I'm not sure of the word), simple, sturdy ; like a tool we can trust.
In the meantime, thinking about colour, I like when colour are different from what we often see (black, grey). I prefer light color (soft grey) and why not some nuance in the grey. Nuance of a warm colour like salmon.
One year ago, I've bought this kind of watch:
I really like the feeling of this device. Just metal and leather. A simple shape. A global identity, not a conglomerate of different pieces put together.
For sure the color is to pronounced, but maybe just a nuance of salmon (or other colors), a warm color that does't feel artificial.