Sorry, newbie. They are the same. You want to believe misinformation, go right ahead. It is a PCGS/ NGC label thing. I have two coins right now that are the identical grade and surface preservation-- one is Dcam, and the other is Ucam. Definitely a Ford-Chevy thing.
Be aware that even though UCAM and DCAM are indicators of the highest level of cameo, these designations are sloppy at best. These designations are vague to the point that a very high level of DCAM or UCAM varies greatly in levels of the same designations. I divide the designations into a 10 point scale for my own satisfaction. Compare DCAM and UCAM Ikes and Kennedys for a wide range of contrast which is quite obvious with several coins of the same date and designation. The same holds for any other proof cameo coin. When the cameo designations were first established in the late 1980s, the intention was to include three separate DCAM designations but the grading services decided to include only one designation for simplicity. The designations should have been DCAM-, DCAM and DCAM+. With all this in mind, there is a huge difference between the appearance, price, and desirability of DCAM andUCAM coins.
Wow, Dan posted misinformation almost 7 years ago, and it dragged down Greg this much later. Object lesson: don't single-source ANYTHING you read online. No editors.
Discovering the information is only half the research. The other half is vetting the sources. We live in a world where spreading disinformation has become an acceptable tactic.