Interesting thread on Quora. I never gave it much thought, although I do have an infographics category, along with a few visualization categories. If I were to take a stab with a sentence I'd say: a visualization is the representation of data via geometry and math while infographics are a subset of visualization, where an actual human being had a hand in explaining the (hopefully interesting) points in the data in question.
Your turn. Sound off in the comments below.