Just to clarify, Dexron is ATF. Assume you are trying to differentiate between Dexron III and Chrysler ATF+4.
From the standpoint of adding fluid, it doesn't matter which is in there. As for changing fluid, you can read the endless threads on the forum and form your own opinion. I believe the latest one was about two weeks ago -- just search "dexron" in the OEM tech forum.
A readily available full synthetic I use is Valvoline High Mileage.