These are the things I have encountered on iPhones ranging from 3G to 6+. I am 99% sure that there is at least one on yours, but it's a good thing if you can't find something wrong or do not consider some of the following as a defect. I wouldn't call everything a defect, as it is a personal preference for some.
- dead pixel
- backlight bleed
- uniformity (one side darker, yellower)
- smudge / smear inside glass
- dust inside screen
- dust or dirt inside glass (outside of screen area)
- recessed / uneven volume button (on one but not another)
- sticky vibration button (normal ones have a nice firm click)
- uneven pressure / sticky / unbalance on sleep wake button (normal ones have a nice click to it)
- uneven home button pressure (perfect ones have a nice click to it, but this is personal preference)
- uneven gap when assembled (run your finger on the edge on each side and compare for your 6/6+)
- dust inside camera lens
- general cosmetic scratches / chips / dings (Apple logo, aluminum, buttons, sim slot)
And this list hasn't even covered technical issues like wifi, Bluetooth, Touch ID, vibration rattle, etc.
But if you can't find anything wrong, be grateful because ignorance is truly a bliss. I envy you!
dL
Huh...I have had a 3, 4, 5 & 6 and thus far, just about flawless.....I guess I never considered it before. I do wish the vibrate mode were not so loud on the 6. Other than that....
I'm grateful!