Emotional appeal works best when you want people to take a desired action. Excitement, urgency…whatever feeling might inspire them to take action, giving people hard-core data will usually not have the same effect.
A 2007 study conducted by Carnegie Mellon University tested response to different appeals for donations for people in dire living situations in Africa. The first appeal gave elaborate statistics on the dislocation of millions of people, food shortages, and the scarcity of rain in the region.
The second appeal talked about the story of a particular girl who was starving in Zambia. A picture of the girl was sent alongside, and students were requested to send donations directly for her.
While the fact-focused appeal got students to donate $1.14 on an average, the amount rose to an average of $2.38 for the story-based appeal. A third appeal that contained both the story and the statistics collected $1.43 on an average.
Source: The WordStream blog, 5/2/13.