CMOS technology, use a NMOS or PMOS as series switch?
I know that NMOS transistors are generally faster than PMOS transistors since electrons have a higher mobility than holes. Therefore NMOS would be preferred over PMOS for applications requiring higher switching frequencies.

However, PMOS transistors have less flicker noise than NMOS because of their smaller transconductance, which means that PMOS conduct less current than NMOS for the same voltage bias and thus generate less noise. Therefore, for applications requiring low noise (such as a precision current mirror), PMOS might be better.