- larger screen - 4" is just enough for me;
- better camera - nice to have but not a must, moreover, it seems slightly protruding;
- barometer - don't need it really;
Price in Europe - 900 euros for 64 GB version without contract.
If I can get iOS8 on my old iPhone 5 then I'll stay with it.
I carry 2 phones so going forward I am looking to use an Android + alternate OS. IPhone is unlikely but not completely ruled out. The bigger screen does help their cause. While I used to have one and liked it I found it a bit plain and overpriced. Going forward I am leaning towards a new OS like Ubuntu/Firefox/Sailfish if I recycle an old Android. And if getting a new 'second' phone it will likely be Windows at the moment as there are some great mid-range phones being released.
Why this thinking; Geek factor, interesting to trying new things, I like giving an underdog a shot, I want to keep my services diversified and I like to feel I'm getting value for money. Naturally it has to work well.