I think that one primary difference between both intellectual movements was their time span. The Harlem Renaissance was mostly concentrated in the 1920s. Its focus and prevalence in the 1920s was designed to add an alternate dimension to the "Roaring '20s." At the same time, the exploration of race and racial identity was commenced with enthusiasm, but also a sort of trepidation. Nothing like this had been done before and there was an intrinsic challenge to expressing it in the Harlem Renaissance. Questions abound as to what should this vision look like, and with the exploration of race already a challenging subject, this added to the challenging diversity of the movement, which some felt prevented its full embrace after the 1920s.
The Chicago Renaissance was more complex in its approach to exploring racial identity. It brought this out through Realism, depicting a condition of race that deliberately embraced its eclectic nature. It embraced its own diverse nature because the time period it spanned did the same. Writers like Wright, Brooks, and Hansberry discussed the issues of race alongside class and social- economic reality. This discussion was reflective of a time period that spanned beyond the 1920s, one that moved into the Great Depression. The continuation of this into the 1930s and beyond enabled more issues connected to racial identity to be explored. In the process, the movement broadened because the discourse did. This helped to sustain the movement into a longer historical context than the Harlem Renaissance.