I've had an issue with signal strength flat-line in my house on my iPhone 5 (AT&T) while my wife's 4S (also AT&T) not changing one bit. So far AT&T has logged two incidents on my phone's signal. I don't get many phone calls and use WiFi at home so it's not a huge deal. AT&T is not that solid in my neighborhood anyway plus, outside my house, the signal is fine. Bottom line it seems to me that, in my situation, iPhone 5 is more finicky about signal strength than the 4S.