We’ve heard enough rah-rah over how much better RSS feeds are than e-mail for online marketing. Show us the proof already.

That’s exactly what Greedy Girl has done. Blogger Kari Sullivan describes herself as “just one girl running several businesses.” After dropping her opt-in e-mail lists and converting all her viral marketing efforts to RSS, Sullivan kept track of the results, which she sums up as “Tons more viral success and a good bit more money.”

Specifically, Sullivan says one RSS subscriber is worth 15-20 e-mail subscribers, her attrition rates are low, her RSS virals get passed on more frequently than e-mails, and Google finds her posts. Why not offer both (which I do)? “I tried that, and it sucked. Only about 5-10% of people chose RSS. I took away the email option, and my RSS subscribers soared.”