"One solo dev who achieves as much as a N-person team" or alternatively, "N developers who achieve as much as a 10*N person team" is the one most easily supported with evidence. Prior to their acquisition, WhatsApp had 55 employees of which 32 were engineers. Facebook Messenger had a team that was most likely 100x larger than that. In 1995 when Microsoft effectively defeated IBM as the premier software company, Microsoft had just 17,000 employees to IBMs 225,000 employees. The entire reason why a startup can even succeed is because a smaller, skilled team can overcome a much larger team with much more resources.