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Security, none of the apps have access to all your data. Android apps have a shocking level of access to things they frankly shouldn't, plus I dislike Google intensely for their lack of privacy and data mining. I go to great lengths to avoid Google, so having a Google o/s would be hell to me.
I also find Android web browsers to be pants.
Other than that, the hardware and o/s on the top line Android devices does everything an iPhone can. Oh and I forgot customisation, but to me that is a load of rubbish. Apple stuff generally works really well out of the box whereas Android phones need me to download and tweak a ton of stuff because the stock items are lousy. Sadly most of the tweaks you can download are lousy too.
 
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