Surprisingly my voice calls on the Xiaomi doesn't last long even on 2G networks while GSMArena rated it 13 hrs talk time on 3G. I noticed when I had a 6 min 2G call, it killed 18% and my battery was 2% worse after an 1 hr SOT from a full charge. My voice calls might only last 5-6 hrs. I will test it turning 3G on while mobile data is off. I doubt it will make any huge difference.
Of course dual wielding phones can remedy all that. I also agree with Jon Rettinger who also uses a OnePlus One and thinks it has the best battery life he ever had on a smartphone (11 hr SOT). I tend to charge my phone every night anyway whether from 1% to 60%. As long as a phone can last ALL DAY without me charging up during mid-afternoons.
For my bare minimum, it should be 8 hrs SOT where I will find it respectable which is around the same time as a typical work day. If I am awake 16 hrs a day, I should hope the 16 hrs get split to work and my smartphone. The only smartphones that ever gave me 8 hrs SOT without breaking a sweat was the iPhone 4 & Mi 3. Almost every other smartphone I owned lasted 4-5 hrs SOT and needed a quick charge each day.
The BEST VALUE AND BATTERY COMBO for 2014 is OnePlus One and Sony Xperia Z3 Compact. That is a potential 25+ hr SOT between them and buying both (sub-$400) can cost as much as one iPhone 6. It is very most complementary to each other. Better than any Samsung Galaxy S5/Note 4, HTC One M8, iPhone 6/6 Plus, or Nexus 6 mix and match combo. The value and battery life is all there as well as big & small.