personally i prefer the warmer screen over the other. The one on my phone is slightly warmer than my 5.
It could be that Accessibility > Reduce White Point and Darken Colors is working better too.
If I had the ability I would instantly install f.lux on my iPhone.
DUDE! I registered to the forum just to say, THANKS! I had forgotten I turned reduce white point on and it was making my screen a blue-ish color that I hated(especially compared to two other iPhones I was holding mine next to). I now have that delicious warm iPhone screen I was hoping for!