We've seen small Raspi clusters (especially for web hosting) frequently on HN, always as proof of concept. But does it really stand out? What about performance/

We've seen small Raspi clusters (especially for web hosting) frequently on HN, always as proof of concept. But does it really stand out? What about performance/(dollar spent on hardware) or (dollar spent on electricity)? How does it compare with an Intel NUC or an Atom/ITX Board?