Actually it's also the LTE. On an Android phone you can actually see the breakdown of the power consumption. Right now I am not in an LTE area, so the phone defaults to 3G - so I can't show you the stats. But when I am in the city, LTE is a major battery drain, even more than the screen.
A week ago I went on a bike ride with a friend. He was toting his brand new i5. Both of us stopped frequently and used maps to check our route. By the end of the 4 hour ride, his phone was at 17% and in the red zone. Mine still had 70% power, thanks to the larger battery and a number of power saving features I had implemented. He had to borrow my phone to call his wife