I used to surprise people on the other end of the line when I told them their iPhone sounded awful would they please exchange it for a Motorola phone. It was so obvious because 1-4 were worse than the worst for outgoing call quality. It is why I never even considered iPhone until I started hearing people on the 4s, which was acceptable. The 5 was the first phone with excellent outgoing quality and the 5s seems identical. The 5c seems less in quality, more like the 4s so I suspect they cheaped out on either the mic or the processing circuitry - or both. I pray the 6 is at least as good as the 5/5s.