It is subjective; I hated the 'design' of the 4 compared to the 'style' of the 3 ... The phone that wiped the floor with all competitors! I upgraded to the 4 because Apple gave people little choice as far as ongoing support ; the same with apps. Hated it though; felt uncomfortable next to the 3 and although the materials were 'more solid', they didn't look and feel as nice IMO. My 3 back cover lasted 3 years whilst the 4 just 2 months, so I laugh when people call plastic like its some cheap nasty material when in fact it is proven to be better than all cases after it! As for the 5 ... Hated it ... Too bland, too boring, not enough difference between the 4 ... and another issue with the scratching and maps! Of course the 4 sold more than the 3 ... The reasons why are pretty clear; but they're nothing to do with its refreshed design.
I have since moved to the S4 - it's a FAR better phone in my opinion; a GLORIOUS screen, fast, great features (love wireless charging and SD expansion) and it feels great in the hand. Yes, it is made of plastic on the back; but I have no issue with this as I had no issue with the iPhone 3. In fact, I refer the pastic back of the S4 to the easily to ruin iPhone 5.
As for all the iPhone users that bitch about the S4 Having a pastic back, that's just desperation in calling the competition; as is calling the display too big or non true to life colours. Even you quote the galaxy as being plastic; highlighting your ignorance and jealousy as far as I'm concerned; and having owned an iPhone 5 previously, all I'll say in reply is you enjoy your metal scratch and dint prone case, your small screen, lack of expansion, wireless charging and outdated OS (which laughably, for ios7, Apple seem to be copying from android and windows. Shameful!!!)
Awaiting silly responses from isheep!