These look to me like carrier (AT&T) not hardware (Apple) problems. No carrier provides uniform service across all markets and locations. By reputation, it is fair to conclude that where AT&T is bad, it is very very bad.
Service in the two or three locations in which one spends most of one's time trumps everything. If AT&T service is bad in your area, you will not be happy with an iPhone.
(There is a solution, the micro-cell, but it is not, and may never be, generally available.)
(I use a Verizon MiFi to reduce my reliance on AT&T. However, this is a limited and expensive solution to what is a fundamental carrier limitation.)