Are you buying the iPhone or iPhone 6 plus. Make sure will it survive if it drops from a certain height?
This is costly so it matters a lot for sure.
You have no need to conduct this test. You just need to check it out. This test has been performed by the David Rahmini on his youtube channel PhoneBuff.
He has dropped the phones number of times with different angles, and with either sides. At the end result is stunning.