So I have my hands on two iPhones (both 16GB black) and did speed tests. One was consistently faster than the other my several fold. The one on the left is a week 31, the one on the right week 27. Both show 4-5 bars. Test 1 Test 2, same as Test 1 but 5 minutes later Test 3, I switched SIM cards, and the phone on the right still remains fast Only about 1/10 of the time could I get the phone on the left to be as fast as the phone on the right, whereas the one on the right was almost always faster.