I am siding with robbo/richdog on this
They are all separate, you have:
- design - the looks i.e. button placement/design, speaker grill, camera lens/flash/speaker design etc. finish of the material
- premium feel - just the general feel of the phone and if it feels expensive
- ergonomics - how the phone feels in the hand in terms of comfort
- durability - how well the phone can survive a drop
- build - how well a phone is put together, does it feel sturdy etc.
Just because a phone is good in one area, doesn't mean that it will be for other areas.
Whilst the GS 3 might feel fantastic in the hand, that isn't because it is made out of plastic, it is largely due to the ergonomic curves, it isn't durable at all due to the design of it i.e. glass extending right to the edge so when you drop it, it is very likely to break since you have a very good chance of the glass edge impacting the ground (sure just look through the gs 3 thread here). With the gs 2, you would have to be very unlucky in order to break it. Lets put it this way, which "finish" would you prefer, the GS 3 plastic finish or the one X plastic finish?
Aluminium is very durable too, the main damage which is caused when dropped is usually down to the finish applied to it i.e. I dropped my one s a month or so ago onto concrete and the aluminium itself is perfectly fine, only the MAO finish came of. Plastic can crack/dent too i.e. didn't mrk post a photo of his note II not long ago where his had some dent/crack on the bottom? But plastic is more durable overall, no denying that. But aluminium isn't as weak as what people are making it out to be.
To me premium feel is about how "expensive/sturdy" the phone feels and there is no way plastic (no matter the finish/manufacturer process or whatever) can match aluminium (especially when it is a uni-body) like on the one S/one etc. I really can't see how anyone can disagree with this. Yes, you might not like how it feels in the hand i.e. cold/hard or whatever but that doesn't mean it isn't premium. Plastic designed phones can have a premium feel to it though i.e. lumia 800 and one X. Every review site always mentions about "premium" quality in their reviews and you can be guaranteed that they always refer to it for the iphones, htc phones etc. never Samsung etc.
All phones have great build quality these days, wouldn't say that one was "much" better than the other, but uni-body do feel much better than non-unibody plastic phones.
Also, the HTC one is being regarded as feeling fantastic in the hand now due to the ergonomic curves, premium feel and having superb build quality (zero gaps etc.). In fact I would imagine that the one will feel just as good, if not better than the gs 3/gs 4 in terms of comfort in the hand, due to the back part being curved as well.