[eulerphi]

Callbacks cause no resource retention other than the closure whereas context switching incurs a much greater hit.

[moe]

Callbacks cause no resource retention

They do cause resource exhaustion in the developer who has to deal with the cascading callback spaghettis.

[justincormack]

Depends what you switch to. Coroutine's just need a C stack for example.

[ori_b]

Cooperative context switching within a process is just a register swap. It's about the same cost as a function call.