Remember the 6 has 10x faster internet with LTE than the 3G iphone 4.  That means more will download before you switch and video will come in higher def, also causing more data.  A study showed going from 3G tech to 4G tech, while "doing the same things" uses 2 to 2.5 times more data than before.  This is across carriers and not just Verizon.  You can confirm by stoppinglooking at Instagram for a whole and see if the data use goes down and your social networking data use goes down.