I visited Xidi and Hongcun in 2017, around the time of Chinese New Year. Both sites were thus very crowded - but on the plus side, most houses were decorated with red "chunlian" banderoles on each side of the door, which enhanced the experience in the otherwise very much black-and-white looking villages. 

Both villages are the most representative villages of the traditional region of Huizhou (where the "hui" part of the name of Anhui province comes from), and are just two of many. The region overall is more or less equivalent to today's Huangshan prefecture and somewhat off the beaten track - but during the Ming and Qing dynasties it was a centre of literati and brought forth many court officials. It was these latter who - once retired from officialdom in Beijing - would build the exquisitely decorated mansions in their home towns in Huizhou. Particularly renowned officials would even be awarded a "paifang" by the emperor - a ceremonial gate, such as the one at the entrance of Xidi.

Xidi, Hongcun and their neighbouring villages were thus relatively wealthy villages, and their architecture is far more elaborate and polished than what would be expected of "vernacular" architecture. In general, the buildings display a pretty plain exterior, which contrasts with extremely ornamented interiors - in particular the interior open-air courtyard which was used to receive guests, where no wooden beam or panel is left undecorated. In addition to wood carving, stone and brick carving are typical of Huizhou architecture, and are also well represented in both sites (in particular in the entry gates of the mansions). These houses - both the main mansions as well as the more intimate houses of lesser families, many of which are still inhabited - were for me the highlight of both sites.

What distinguishes both villages? Hongcun's Moon Pond is certainly picturesque, and its mansions grander, but Xidi overall felt more homely. It's definitely worth visiting both (they're pretty close to each other anyway), and a great addition to China's WHS list beyond the more well-known imperial or religious architecture.