[throwaway197812]

I doubt you'll ever come to a consensus by trying to think of pros and cons and make some kind of objective decision. Unless you're comparing languages that are very specialized for a certain domain, or obviously at opposite ends of the "abstraction continuum" (e.g., C vs. Haskell), it's going to come down to taste and the subjective preferences of the individual developers. As you've discovered, some developers want a stable, boring, mature language that doesn't get in the way of solving the problem; others like the hot new language even if they'll have to fight with the wrinkles yet to be worked out, and struggle with an ecosystem that is shifting under their feet.

Just tell them that whoever gets the prototype working first picks the tech stack.