In Manchester code each bit of data is signified by at least one transition. Manchester encoding is therefore considered to be self-clocking, which means that accurate clock recovery from a data stream is possible. In addition, the DC component of the encoded signal is zero. Although transitions allow the signal to be self-clocking, it carries significant overhead as there is a need for essentially twice the bandwidth of a simple NRZ or NRZI encoding.
Unipolar most of signal power is centered on origin and there is waste of power due to DC component that is present.
Polar format most of signal power is centered on origin and they are simple to implement.
Bipolar format does not have DC component and does not demand more bandwidth, but power requirement is double than other formats.
Manchester format does not have DC component but provides proper clocking.