[theptip]

If you are starting a business, use whatever language you already know. The benefits of one framework vs. the other are a rounding error compared to language fluency. (They are both great, in other words.)

If you are learning both language and framework from scratch, check the local job market. 5 years ago in the Bay Area there were roughly 2x as many Rails job postings as Django, though I doubt it is this lopsided now. Also Python is used more broadly than Ruby, eg for ML and scientific/numeric work.