What should i chose?

Solution
Of these two, I would choose the Core i5 + R9 280.
The better CPU will mean more consistent performance in all games, and better performance in any other applications.
The slightly slower GPU will mean slightly lower frame rates, but you can always lower graphics settings if higher frame rates are desired.
Graphics card technology improves much faster than CPU performance as well, so you will find you want to upgrade your graphics card before your CPU and the Core i5 will give you much better performance with the new card as well.
Of these two, I would choose the Core i5 + R9 280.
The better CPU will mean more consistent performance in all games, and better performance in any other applications.
The slightly slower GPU will mean slightly lower frame rates, but you can always lower graphics settings if higher frame rates are desired.
Graphics card technology improves much faster than CPU performance as well, so you will find you want to upgrade your graphics card before your CPU and the Core i5 will give you much better performance with the new card as well.
 
Solution