Ok I think that every phone ever made does not fare well if sat on. That is why I never understood people putting phones in there back pocket. You can say what you want about the iPhone, but the build is one of the best if not the best. Please tell me a better phone build wise?
Build wise? What do you mean by that? Design? Strength? Both?
In general, I prefer the design of the One X over any other phones in both categories. Very solid phone with a beautiful design.
At the end, it's opinions. You say the iPhone is designed best but not everyone will say the same.
As for people putting their phones in their back pocket. They do it because it was ok with previous phones.
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My Nexus has weird scuff marks all over the plastic body. I don't know where they came from or why they won't go away, but it's enough to convince me that plastic loses its aesthetic appeal after a few weeks.
Most materials scuffs, just look at the amount of threads here discussing about scuffs on the iPhone 5.