A big factor, 4G being used or not, that a lot of people fail to take into account, is signal strength.
The closer you are to a tower (or the stronger your signal), the less wattage your phone puts out in signal.
The further you are from a tower (or deeper inside a building that reduces your signal), the more wattage is output to account for the additional "distance" to the tower.
The funny thing is, my job is just 2 blocks from a tower, and my home is about 3 miles from the closest one. You would think that while at work I would get better signal (which would equate to better battery life) - I don't. Because of the construction of our office building, I get very low (but still very usable) inside. Because of this, I use battery faster in the office than I do at home.
Make sense?