In my experience the key difference is that managers often accept they are part of an inherently soulless capitalistic exchange of their time for money. Many ICs prefer the illusion that they're not. Everything else tends to flow from that. A manager with that illusion will not rise up as quickly and an IC without that illusion will rise up more quickly. Of course living life without that illusion is not inherently better (except for the money) since it can feel very soul destroying.