Ming runs the sharpest Science-versus-government trade-off of the Exploration Age — an enormous Capital Science bonus that shrinks with every Social Policy you slot, forcing genuinely different choices than any other civilization.
"Great Canon of Yongle" grants a large Science bonus in the Capital, but reduces Science per turn for every Social Policy (not Tradition) currently slotted in your government — the penalty specifically exempts Traditions, so a government built around Traditions rather than standard Policies avoids most of the downside.
The Mandarin is a unique Merchant unit that adds a large amount of Gold whenever it uses the Create a Road action, turning routine infrastructure work into a genuine income source. The Xunleichong is a unique Infantry unit with a Ranged attack and increased Combat Strength on Featureless terrain, stronger still when grouped together on flat ground.
The Ming Great Wall is a unique, Ageless Improvement that counts as a Fortification and grants extra Gold for adjacent Fortifications, though it can only be built in a line. The associated Wonder, the Forbidden City, grants Culture and boosts Culture on all Fortification Buildings, and must be built adjacent to a District.