Don't be fooled, HD radio or "hybrid-digital" is a low resolution format. It is sort of like hearing the sound coming out of a tin can.

FM stations can carry information at 96 kbit/s or 128 kbit/s it uses a really stupid proprietary compression algorithm that the radio stations pay a royalty to iBiquity to use. Standard FM radio sounds way better because of the ludicrous level of compression used.

While in hybrid mode, an HD Radio will lock onto an analog signal first in mono, then stereo, then try to find a digital one. There is a reason for that, it sucks.

Try listening to BBC radio from their site over the internet to get an idea of the quality.