What are the advantages of using NMOS inverter instead of CMOS?

CMOS circuits utilize complementary MOSFETs, i.e; NMOS and PMOS devices together in various patterns to create functional blocks like AND or OR gates. However the problem with these types of CMOS circuits is that they are inherently low power circuits. They cannot handle large currents. So when your block needs to have a large fan out (need to drive a large no of outputs, i.e; more current required) CMOS circuits fail. That is why we use BiCMOS. They are very similar to CMOS circuits except for the BJT(Bipolar Junction Transistor) output stage. BJTs are capable of carrying large currents, hence BiCMOS circuits are used in cases of large current requirements.