You were correct in your original thinking. However, we are dealing with audio coming out of a scanner. Most scanners do not fit the audiophile's definition of high end audio equipment, i.e. high fidelity.
Scanners do not produce audio on par with CD players or even an FM radio. Most of this has to do with the fact that the signals they are receiving are narrowband voice comms never intended for high fidelity in the first place. The other part is, the manufacturers of scanners really don't give a crap.
So by using a really high bit rate, you are not improving the quality of the scanner audio, just using more bandwidth. I would stick with 16. You can try 12, but I have a feeling you'll put it back at 16. I am listening to your feed right now and it sounds just fine.
The reason why you feel the lower bit rate sounds better is possibly because you are noticing the deficiencies (pardon my spelling; on my second margarita...viva cinco de Mayo!!) in the scanner audio. The compression helps mask these, and therefor it may actually sound "better".
Good job on your feed.
Ryan