[notacoward]

There's often a third possibility; leaving groups. At a small enough startup they're effectively the same, but I've seen distinct groups form in companies as small as 20. While it's true that a manager can affect the quality of the entire group, they're only one factor. High-performing fun group with a ho-hum manager? I'll probably stay. Dysfunctional bunch of ho-hum peers with a really good manager? That was my last job, and it's not my current job for exactly that reason.

Especially at a larger company, managers might be constrained wrt hiring and firing, reviews and raises, pushing back against misguided product-management decisions, etc. Even a good manager might not be able to deal with these issues quickly enough to prevent attrition. I've seen some really good managers, people I'd worked with before and who have been superstars at other companies, burn out trying. That's sort of leaving the company that hobbled the manager, but other managers and other groups within the same company were doing fine so I'd call it leaving the group.