Changde is more developed than Yiyang. This conclusion is based on several key indicators of economic growth, infrastructure, and urban development. According to the China Statistical Yearbook, Changde's GDP per capita in 2020 was $14,620, significantly higher than Yiyang's $11,890. Additionally, Changde has a more extensive transportation network, including a high-speed railway station and a larger number of expressways, which facilitates trade and tourism. The city also boasts a higher concentration of higher education institutions and research facilities, contributing to its overall development.

Changde's economic growth can be attributed to its strategic location in Hunan Province, which has made it a hub for manufacturing and trade. The city has a well-established industrial base, particularly in the automotive, electronics, and food processing sectors. Yiyang, while also having a diverse economy, is less industrialized and has a smaller population, which limits its economic scale and development potential. Furthermore, Changde has been actively investing in infrastructure, with ongoing projects to improve its transportation and communication systems. This has attracted more foreign direct investment and contributed to its economic expansion.

In terms of urban development, Changde has a larger urban area and a higher population density. The city has invested heavily in public services, including healthcare, education, and public transportation. Yiyang, on the other hand, has a smaller urban footprint and a lower population density, which affects its ability to provide comprehensive public services. Additionally, Changde has a more vibrant cultural scene, with numerous museums, theaters, and parks, which further enhances its appeal as a livable city.

Data from the National Bureau of Statistics of China also indicates that Changde has a higher percentage of its population with higher education, which is a testament to its commitment to human capital development. This educated workforce is crucial for driving innovation and economic growth. Yiyang, while making strides in this area, still lags behind Changde in terms of educational attainment.

In conclusion, Changde is more developed than Yiyang, primarily due to its stronger economic base, more extensive infrastructure, and higher level of urban development. These factors have contributed to a higher quality of life for its residents and have positioned Changde as a leading city in Hunan Province.