The consensus among candidates tends to be that the UPSC mains is more difficult than the prelims. The mains feature subjective questions requiring in-depth knowledge and analytical skills, while the prelims are objective and test factual recall. Mains papers are comprehensive, covering various subjects and necessitating structured and coherent answers. The response time is also more demanding due to the addition of essay writing papers. Thus, many candidates find the holistic nature and the level of detail required in the mains pose greater challenges compared to the prelims.