Apparently iPhone 7(+) does not have the antennas for 4x4 MIMO / 256 QAM which the Samsung S7 does provide for. http://cellularinsights.com/samsung-galaxy-s7-the-first-4x4-...
https://news.ycombinator.com/item?id=12678124
LG V20 which should be shipping by end of Oct does support AWS-3 (Band 66) http://cellularinsights.com/lg-v20-the-first-aws-3-capable-s...
These issues are important to extend signal and to make better use of spectrum in areas with large buildings and high population density.