The irony is that hypervisors and containers have basically taken away whatever benefits monolithic kernels might have.
OS X and Windows are much better in this regard than GNU/Linux/BSDs with their ongoing efforts to move all drivers to userspace, even though they will never be fully pure microkernels when done with it.
He, true. Although I wonder if microkernels tend to expose more lower level function in user mode that could be relevant to overall system security. The big problem is probably memory access, which would be prohibited in user mode, but maybe there are other security implications (I couldn't answer that question).
Other than improved security that may also be protected by a hypervisor, you might still gain more stability when pushing drivers to user mode. Or your hypervisor has a bug and allows a guest to gain privileged kernel access. Not a security expert, so this is mainly guess work.
OS X and Windows are much better in this regard than GNU/Linux/BSDs with their ongoing efforts to move all drivers to userspace, even though they will never be fully pure microkernels when done with it.