Hi Tom, I have an II and three III radios.
the II is a better radio for sensitivity and selectivity.  It has better
image rejection from strong stations, and better side rejection.
If you are however listening to a station that is clear on both radios, I
find the III has a fuller more comfortable audio.  They both are just
average on FM.
The III has a wide band AM listening position, which if you plug the radio
into a good system, really shines.

So in summary the II is a better radio if you want to listen to WJR in
Milwaukee in the daytime, but on the other hand, who wants to do that?