When I photographed the American Heart Association's Washington, D.C. Heart Walk, the light was extremely diffuse. In fact, there was a light rain most of the time. When it comes to making informal candids and posed photos, I'll take diffuse light any time over contrasting light. Some people would understandably use a flash with a diffuser attached to brighten the subjects, but I usually prefer the look shown below made without flash.
Photo #1 (candid)
Photo #2 (posed)
Photo #3 (candid)
Photo #4 (posed)