Although that argument only works if you stereotype things completely. On one side we have a savvy outspoken salesman and on the other a shy introvert coder. And each thinks the other is completely replaceable. Kind of black/white don't you think?

Thats sort of the VC mental model i.e. the mantra that more people in the team makes it more likely that the startup has the entire skillset needed to create a successful business. On the other hand - one of the top reasons for startups failing is cofounder disputes. So difficult to say - are more founders less or more risky? :)

Most serial founders I know are actually pretty good at multiple things - experience and endless pitches will often do that to you.