Both are becoming exceedingly rare. Now, conservative Republicans, almost as endangered as moderate Republicans have both. Right wing Republicans have neither. Progressive Democrats, a largr number, often lack common sense.
SO, I have to go with common decency.
Uncommon sense is the thing of the day.....
common decency is slightly more common, but not nearly common enough.
more common is decency...
Common people. It takes common sense to realize no one shows any common decency anymore.
Neither really matter in the end.