I live in a densely populated area with very few open FM channels and agree about the sound quality. Bluetooth with AUX is the best transmission quality. Another tip: when playing music through Bluetooth, set your phone's volume around 90% and the music will be clearer than if it is set to 100%.
What he said. I discovered that a long time ago too. Setting the phone (at least the iPhones I've owned) to 100% overdrives the output circuits of the headphone amp, and causes distortion. I recall reading at some point several years ago that the iPhone uses some kind of dynamically adjusted equalization for the headphone amp to better match human hearing response as volume increases, so by definition, it "distorts" the output as volume increases. Based on my playing with the volume output through the Bluetooth connection, I'm pretty sure the same equalization is applied to that output too. In fact, I think 80% volume sounds more natural than 90%.