What does iOS have to do with US vs Non-US customers ? iOS is made for ONE family of devices, all with the same hardware per iteration and Apple only have to worry about that one family, with is like... what... maybe four different phones being actively supported at this point ?
If OS updates are your priority, get the Nexus 4 or another "nexus" device - then you'll get updates with iOS frequency and support. It depends on what is important to you.
I'd rather have the 2Gb RAM than the quadcore.
Developers do a great job of keeping a phone "alive" and making it even better than stock so I think it's a safe bet that any popular device (like the S3) will have a long "second life" in development even after official updates are no longer pushed.
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