So Xperia Z5 or Xperia Z5 Premium

I know the phones are yet to be reviewed but which one should I lean towards to. In my country if you preorder one you get free 100e headphones for free, so Im considering preordering one of the two. I like the idea of bigger screen on Z5 Premium and would definitely buy that but Im concerned about the performance and battery life. Do you think that the fact that only media is displayed in 4k helps with performance to be as fast as "normal" Z5?

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